diff --git a/.travis.yml b/.travis.yml
index e12bc0c..f857063 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -19,75 +19,23 @@
     "include": [
       {
         "env": "BUILD=style",
-        "python": "3.6"
+        "python": "3.7"
       },
       {
         "env": "BUILD=test REQUIREMENTS=release",
-        "python": "3.5"
-      },
-      {
-        "dist": "trusty",
-        "env": "BUILD=test-storage DAV_SERVER=radicale REQUIREMENTS=release ",
-        "python": "3.5"
-      },
-      {
-        "dist": "trusty",
-        "env": "BUILD=test-storage DAV_SERVER=xandikos REQUIREMENTS=release ",
-        "python": "3.5"
-      },
-      {
-        "env": "BUILD=test REQUIREMENTS=minimal",
-        "python": "3.5"
-      },
-      {
-        "dist": "trusty",
-        "env": "BUILD=test-storage DAV_SERVER=radicale REQUIREMENTS=minimal ",
-        "python": "3.5"
-      },
-      {
-        "dist": "trusty",
-        "env": "BUILD=test-storage DAV_SERVER=xandikos REQUIREMENTS=minimal ",
-        "python": "3.5"
-      },
-      {
-        "env": "BUILD=test REQUIREMENTS=release",
-        "python": "3.6"
+        "python": "3.7"
       },
       {
         "env": "BUILD=test-storage DAV_SERVER=radicale REQUIREMENTS=release ",
-        "python": "3.6"
+        "python": "3.7"
       },
       {
         "env": "BUILD=test-storage DAV_SERVER=xandikos REQUIREMENTS=release ",
-        "python": "3.6"
+        "python": "3.7"
       },
       {
         "env": "BUILD=test-storage DAV_SERVER=fastmail REQUIREMENTS=release ",
         "if": "NOT (type IN (pull_request))",
-        "python": "3.6"
-      },
-      {
-        "env": "BUILD=test REQUIREMENTS=minimal",
-        "python": "3.6"
-      },
-      {
-        "env": "BUILD=test-storage DAV_SERVER=radicale REQUIREMENTS=minimal ",
-        "python": "3.6"
-      },
-      {
-        "env": "BUILD=test-storage DAV_SERVER=xandikos REQUIREMENTS=minimal ",
-        "python": "3.6"
-      },
-      {
-        "env": "BUILD=test REQUIREMENTS=release",
-        "python": "3.7"
-      },
-      {
-        "env": "BUILD=test-storage DAV_SERVER=radicale REQUIREMENTS=release ",
-        "python": "3.7"
-      },
-      {
-        "env": "BUILD=test-storage DAV_SERVER=xandikos REQUIREMENTS=release ",
         "python": "3.7"
       },
       {
@@ -128,7 +76,7 @@
       },
       {
         "env": "BUILD=test ETESYNC_TESTS=true REQUIREMENTS=latest",
-        "python": "3.6"
+        "python": "3.7"
       }
     ]
   },
diff --git a/docs/conf.py b/docs/conf.py
index 385d2e8..5fe5e51 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -65,7 +65,7 @@ def github_issue_role(name, rawtext, text, lineno, inliner,
         if issue_num <= 0:
             raise ValueError()
     except ValueError:
-        msg = inliner.reporter.error('Invalid GitHub issue: {}'.format(text),
+        msg = inliner.reporter.error(f'Invalid GitHub issue: {text}',
                                      line=lineno)
         prb = inliner.problematic(rawtext, rawtext, msg)
         return [prb], [msg]
diff --git a/docs/installation.rst b/docs/installation.rst
index 7690f2d..2d33c57 100644
--- a/docs/installation.rst
+++ b/docs/installation.rst
@@ -41,7 +41,7 @@ If your distribution doesn't provide a package for vdirsyncer, you still can
 use Python's package manager "pip". First, you'll have to check that the
 following things are installed:
 
-- Python 3.5+ and pip.
+- Python 3.7+ and pip.
 - ``libxml`` and ``libxslt``
 - ``zlib``
 - Linux or OS X. **Windows is not supported**, see :gh:`535`.
diff --git a/scripts/make_travisconf.py b/scripts/make_travisconf.py
index 07f4342..3e5882d 100755
--- a/scripts/make_travisconf.py
+++ b/scripts/make_travisconf.py
@@ -3,8 +3,7 @@
 import itertools
 import json
 
-python_versions = ("3.5", "3.6", "3.7", "3.8")
-latest_python = "3.6"
+python_versions = ["3.7", "3.8"]
 
 cfg = {}
 
@@ -34,7 +33,7 @@ matrix = []
 cfg['matrix'] = {'include': matrix, 'fast_finish': True}
 
 matrix.append({
-    'python': latest_python,
+    'python': python_versions[0],
     'env': 'BUILD=style'
 })
 
@@ -51,7 +50,7 @@ for python, requirements in itertools.product(
         'env': f"BUILD=test REQUIREMENTS={requirements}",
     })
 
-    if python == latest_python and requirements == "release":
+    if python == python_versions[0] and requirements == "release":
         dav_servers += ("fastmail",)
 
     for dav_server in dav_servers:
@@ -61,8 +60,6 @@ for python, requirements in itertools.product(
                     f"DAV_SERVER={dav_server} "
                     f"REQUIREMENTS={requirements} ")
         }
-        if python == '3.5':
-            job['dist'] = 'trusty'
 
         build_prs = dav_server not in ("fastmail", "davical", "icloud")
         if not build_prs:
@@ -71,7 +68,7 @@ for python, requirements in itertools.product(
         matrix.append(job)
 
 matrix.append({
-    'python': latest_python,
+    'python': python_versions[0],
     'env': ("BUILD=test "
             "ETESYNC_TESTS=true "
             "REQUIREMENTS=latest")
diff --git a/setup.py b/setup.py
index 653be04..9221367 100644
--- a/setup.py
+++ b/setup.py
@@ -87,8 +87,6 @@ setup(
         'License :: OSI Approved :: BSD License',
         'Operating System :: POSIX',
         'Programming Language :: Python :: 3',
-        'Programming Language :: Python :: 3.5',
-        'Programming Language :: Python :: 3.6',
         'Programming Language :: Python :: 3.7',
         'Programming Language :: Python :: 3.8',
         'Topic :: Internet',
diff --git a/tests/storage/__init__.py b/tests/storage/__init__.py
index dd0d0b3..b268972 100644
--- a/tests/storage/__init__.py
+++ b/tests/storage/__init__.py
@@ -19,7 +19,7 @@ from .. import EVENT_TEMPLATE, TASK_TEMPLATE, VCARD_TEMPLATE, \
 
 def get_server_mixin(server_name):
     from . import __name__ as base
-    x = __import__('{}.servers.{}'.format(base, server_name), fromlist=[''])
+    x = __import__(f'{base}.servers.{server_name}', fromlist=[''])
     return x.ServerMixin
 
 
@@ -183,7 +183,7 @@ class StorageTests:
     def test_discover(self, requires_collections, get_storage_args, get_item):
         collections = set()
         for i in range(1, 5):
-            collection = 'test{}'.format(i)
+            collection = f'test{i}'
             s = self.storage_class(**get_storage_args(collection=collection))
             assert not list(s.list())
             s.upload(get_item())
diff --git a/tests/system/cli/test_repair.py b/tests/system/cli/test_repair.py
index cad41f6..d3c05cf 100644
--- a/tests/system/cli/test_repair.py
+++ b/tests/system/cli/test_repair.py
@@ -19,7 +19,7 @@ def storage(tmpdir, runner):
 def test_basic(storage, runner, collection):
     if collection is not None:
         storage = storage.mkdir(collection)
-        collection_arg = 'foo/{}'.format(collection)
+        collection_arg = f'foo/{collection}'
     else:
         collection_arg = 'foo'
 
diff --git a/tests/system/cli/test_sync.py b/tests/system/cli/test_sync.py
index 97e21e8..e84d798 100644
--- a/tests/system/cli/test_sync.py
+++ b/tests/system/cli/test_sync.py
@@ -461,7 +461,7 @@ def test_partial_sync(tmpdir, runner, partial_sync):
     fileext = ".txt"
     path = "{base}/bar"
     '''.format(
-        partial_sync=('partial_sync = "{}"\n'.format(partial_sync)
+        partial_sync=(f'partial_sync = "{partial_sync}"\n'
                       if partial_sync else ''),
         base=str(tmpdir)
     )))
diff --git a/tests/unit/cli/test_fetchparams.py b/tests/unit/cli/test_fetchparams.py
index 2d28507..9339066 100644
--- a/tests/unit/cli/test_fetchparams.py
+++ b/tests/unit/cli/test_fetchparams.py
@@ -47,7 +47,7 @@ def test_key_conflict(monkeypatch, mystrategy):
 @given(s=st.text(), t=st.text(min_size=1))
 def test_fuzzing(s, t, mystrategy):
     config = expand_fetch_params({
-        '{}.fetch'.format(s): ['mystrategy', t]
+        f'{s}.fetch': ['mystrategy', t]
     })
 
     assert config[s] == t
diff --git a/tests/unit/sync/test_sync.py b/tests/unit/sync/test_sync.py
index 4e9651f..4d554c5 100644
--- a/tests/unit/sync/test_sync.py
+++ b/tests/unit/sync/test_sync.py
@@ -253,7 +253,7 @@ def test_conflict_resolution_both_etags_new(winning_storage):
     b.update(href_b, item_b, etag_b)
     with pytest.raises(SyncConflict):
         sync(a, b, status)
-    sync(a, b, status, conflict_resolution='{} wins'.format(winning_storage))
+    sync(a, b, status, conflict_resolution=f'{winning_storage} wins')
     assert items(a) == items(b) == {
         item_a.raw if winning_storage == 'a' else item_b.raw
     }
@@ -563,7 +563,7 @@ class SyncMachine(RuleBasedStateMachine):
           uid=uid_strategy,
           etag=st.text())
     def upload(self, storage, uid, etag):
-        item = Item('UID:{}'.format(uid))
+        item = Item(f'UID:{uid}')
         storage.items[uid] = (etag, item)
 
     @rule(storage=Storage, href=st.text())
diff --git a/tests/unit/test_repair.py b/tests/unit/test_repair.py
index 5467c54..b444d0b 100644
--- a/tests/unit/test_repair.py
+++ b/tests/unit/test_repair.py
@@ -18,11 +18,11 @@ def test_repair_uids(uid):
     s.items = {
         'one': (
             'asdf',
-            Item('BEGIN:VCARD\nFN:Hans\nUID:{}\nEND:VCARD'.format(uid))
+            Item(f'BEGIN:VCARD\nFN:Hans\nUID:{uid}\nEND:VCARD')
         ),
         'two': (
             'asdf',
-            Item('BEGIN:VCARD\nFN:Peppi\nUID:{}\nEND:VCARD'.format(uid))
+            Item(f'BEGIN:VCARD\nFN:Peppi\nUID:{uid}\nEND:VCARD')
         )
     }
 
@@ -40,7 +40,7 @@ def test_repair_uids(uid):
 @settings(suppress_health_check=HealthCheck.all())
 def test_repair_unsafe_uids(uid):
     s = MemoryStorage()
-    item = Item('BEGIN:VCARD\nUID:{}\nEND:VCARD'.format(uid))
+    item = Item(f'BEGIN:VCARD\nUID:{uid}\nEND:VCARD')
     href, etag = s.upload(item)
     assert s.get(href)[0].uid == uid
     assert not href_safe(uid)
@@ -58,7 +58,7 @@ def test_repair_unsafe_uids(uid):
     ('perfectly-fine', 'b@dh0mbr3')
 ])
 def test_repair_unsafe_href(uid, href):
-    item = Item('BEGIN:VCARD\nUID:{}\nEND:VCARD'.format(uid))
+    item = Item(f'BEGIN:VCARD\nUID:{uid}\nEND:VCARD')
     new_item = repair_item(href, item, set(), True)
     assert new_item.raw != item.raw
     assert new_item.uid != item.uid
diff --git a/tests/unit/utils/test_vobject.py b/tests/unit/utils/test_vobject.py
index 84d87a8..d029ed9 100644
--- a/tests/unit/utils/test_vobject.py
+++ b/tests/unit/utils/test_vobject.py
@@ -221,7 +221,7 @@ def test_replace_uid(template, uid):
     item = vobject.Item(template.format(r=123, uid=123)).with_uid(uid)
     assert item.uid == uid
     if uid:
-        assert item.raw.count('\nUID:{}'.format(uid)) == 1
+        assert item.raw.count(f'\nUID:{uid}') == 1
     else:
         assert '\nUID:' not in item.raw
 
@@ -317,7 +317,7 @@ class VobjectMachine(RuleBasedStateMachine):
           params=st.lists(st.tuples(value_strategy, value_strategy)))
     def add_prop_raw(self, c, key, value, params):
         params_str = ','.join(k + '=' + v for k, v in params)
-        c.props.insert(0, '{};{}:{}'.format(key, params_str, value))
+        c.props.insert(0, f'{key};{params_str}:{value}')
         assert c[key] == value
         assert key in c
         assert c.get(key) == value
diff --git a/vdirsyncer/__init__.py b/vdirsyncer/__init__.py
index 84dbb69..dbdd529 100644
--- a/vdirsyncer/__init__.py
+++ b/vdirsyncer/__init__.py
@@ -19,8 +19,8 @@ except ImportError:  # pragma: no cover
 
 def _check_python_version():  # pragma: no cover
     import sys
-    if sys.version_info < (3, 4, 0):
-        print('vdirsyncer requires at least Python 3.5.')
+    if sys.version_info < (3, 7, 0):
+        print('vdirsyncer requires at least Python 3.7.')
         sys.exit(1)
 
 
diff --git a/vdirsyncer/cli/__init__.py b/vdirsyncer/cli/__init__.py
index 116759a..8f0e4e0 100644
--- a/vdirsyncer/cli/__init__.py
+++ b/vdirsyncer/cli/__init__.py
@@ -65,7 +65,7 @@ def max_workers_callback(ctx, param, value):
     if value == 0 and logging.getLogger('vdirsyncer').level == logging.DEBUG:
         value = 1
 
-    cli_logger.debug('Using {} maximal workers.'.format(value))
+    cli_logger.debug(f'Using {value} maximal workers.')
     return value
 
 
@@ -75,7 +75,7 @@ def max_workers_option(default=0):
         help += 'The default is 0, which means "as many as necessary". ' \
                 'With -vdebug enabled, the default is 1.'
     else:
-        help += 'The default is {}.'.format(default)
+        help += f'The default is {default}.'
 
     return click.option(
         '--max-workers', default=default, type=click.IntRange(min=0, max=None),
diff --git a/vdirsyncer/cli/config.py b/vdirsyncer/cli/config.py
index 643e506..3e74420 100644
--- a/vdirsyncer/cli/config.py
+++ b/vdirsyncer/cli/config.py
@@ -101,7 +101,7 @@ class _ConfigReader:
     def _parse_section(self, section_type, name, options):
         validate_section_name(name, section_type)
         if name in self._seen_names:
-            raise ValueError('Name "{}" already used.'.format(name))
+            raise ValueError(f'Name "{name}" already used.')
         self._seen_names.add(name)
 
         if section_type == 'general':
@@ -163,7 +163,7 @@ class Config:
             try:
                 self.pairs[name] = PairConfig(self, name, options)
             except ValueError as e:
-                raise exceptions.UserError('Pair {}: {}'.format(name, e))
+                raise exceptions.UserError(f'Pair {name}: {e}')
 
     @classmethod
     def from_fileobject(cls, f):
diff --git a/vdirsyncer/cli/discover.py b/vdirsyncer/cli/discover.py
index 30addc3..b3bff73 100644
--- a/vdirsyncer/cli/discover.py
+++ b/vdirsyncer/cli/discover.py
@@ -211,7 +211,7 @@ def _print_collections(instance_name, get_discovered):
         logger.warning('Failed to discover collections for {}, use `-vdebug` '
                        'to see the full traceback.'.format(instance_name))
         return
-    logger.info('{}:'.format(instance_name))
+    logger.info(f'{instance_name}:')
     for args in discovered.values():
         collection = args['collection']
         if collection is None:
@@ -226,7 +226,7 @@ def _print_collections(instance_name, get_discovered):
 
         logger.info('  - {}{}'.format(
             json.dumps(collection),
-            ' ("{}")'.format(displayname)
+            f' ("{displayname}")'
             if displayname and displayname != collection
             else ''
         ))
diff --git a/vdirsyncer/cli/fetchparams.py b/vdirsyncer/cli/fetchparams.py
index 346a14f..801d599 100644
--- a/vdirsyncer/cli/fetchparams.py
+++ b/vdirsyncer/cli/fetchparams.py
@@ -19,7 +19,7 @@ def expand_fetch_params(config):
 
         newkey = key[:-len(SUFFIX)]
         if newkey in config:
-            raise ValueError('Can\'t set {} and {}.'.format(key, newkey))
+            raise ValueError(f'Can\'t set {key} and {newkey}.')
         config[newkey] = _fetch_value(config[key], key)
         del config[key]
 
@@ -45,7 +45,7 @@ def _fetch_value(opts, key):
     cache_key = tuple(opts)
     if cache_key in password_cache:
         rv = password_cache[cache_key]
-        logger.debug('Found cached value for {!r}.'.format(opts))
+        logger.debug(f'Found cached value for {opts!r}.')
         if isinstance(rv, BaseException):
             raise rv
         return rv
@@ -54,7 +54,7 @@ def _fetch_value(opts, key):
     try:
         strategy_fn = STRATEGIES[strategy]
     except KeyError:
-        raise exceptions.UserError('Unknown strategy: {}'.format(strategy))
+        raise exceptions.UserError(f'Unknown strategy: {strategy}')
 
     logger.debug('Fetching value for {} with {} strategy.'
                  .format(key, strategy))
diff --git a/vdirsyncer/cli/tasks.py b/vdirsyncer/cli/tasks.py
index da7adc5..7cadaf2 100644
--- a/vdirsyncer/cli/tasks.py
+++ b/vdirsyncer/cli/tasks.py
@@ -45,7 +45,7 @@ def sync_collection(wq, collection, general, force_delete):
     status_name = get_status_name(pair.name, collection.name)
 
     try:
-        cli_logger.info('Syncing {}'.format(status_name))
+        cli_logger.info(f'Syncing {status_name}')
 
         a = storage_instance_from_config(collection.config_a)
         b = storage_instance_from_config(collection.config_b)
@@ -110,7 +110,7 @@ def repair_collection(config, collection, repair_unsafe_uid):
     config['type'] = storage_type
     storage = storage_instance_from_config(config)
 
-    cli_logger.info('Repairing {}/{}'.format(storage_name, collection))
+    cli_logger.info(f'Repairing {storage_name}/{collection}')
     cli_logger.warning('Make sure no other program is talking to the server.')
     repair_storage(storage, repair_unsafe_uid=repair_unsafe_uid)
 
@@ -121,7 +121,7 @@ def metasync_collection(wq, collection, general):
     status_name = get_status_name(pair.name, collection.name)
 
     try:
-        cli_logger.info('Metasyncing {}'.format(status_name))
+        cli_logger.info(f'Metasyncing {status_name}')
 
         status = load_status(general['status_path'], pair.name,
                              collection.name, data_type='metadata') or {}
diff --git a/vdirsyncer/cli/utils.py b/vdirsyncer/cli/utils.py
index 765c411..46e37f2 100644
--- a/vdirsyncer/cli/utils.py
+++ b/vdirsyncer/cli/utils.py
@@ -144,11 +144,11 @@ def handle_cli_error(status_name=None, e=None):
         import traceback
         tb = traceback.format_tb(tb)
         if status_name:
-            msg = 'Unknown error occurred for {}'.format(status_name)
+            msg = f'Unknown error occurred for {status_name}'
         else:
             msg = 'Unknown error occurred'
 
-        msg += ': {}\nUse `-vdebug` to see the full traceback.'.format(e)
+        msg += f': {e}\nUse `-vdebug` to see the full traceback.'
 
         cli_logger.error(msg)
         cli_logger.debug(''.join(tb))
@@ -210,8 +210,7 @@ def manage_sync_status(base_path, pair_name, collection_name):
         with open(path, 'rb') as f:
             if f.read(1) == b'{':
                 f.seek(0)
-                # json.load doesn't work on binary files for Python 3.5
-                legacy_status = dict(json.loads(f.read().decode('utf-8')))
+                legacy_status = dict(json.load(f))
     except (OSError, ValueError):
         pass
 
@@ -247,7 +246,7 @@ def storage_class_from_config(config):
         cls = storage_names[storage_name]
     except KeyError:
         raise exceptions.UserError(
-            'Unknown storage type: {}'.format(storage_name))
+            f'Unknown storage type: {storage_name}')
     return cls, config
 
 
@@ -399,7 +398,7 @@ def handle_collection_not_found(config, collection, e=None):
     storage_name = config.get('instance_name', None)
 
     cli_logger.warning('{}No collection {} found for storage {}.'
-                       .format('{}\n'.format(e) if e else '',
+                       .format(f'{e}\n' if e else '',
                                json.dumps(collection), storage_name))
 
     if click.confirm('Should vdirsyncer attempt to create it?'):
diff --git a/vdirsyncer/exceptions.py b/vdirsyncer/exceptions.py
index 5644b54..b21cd27 100644
--- a/vdirsyncer/exceptions.py
+++ b/vdirsyncer/exceptions.py
@@ -10,7 +10,7 @@ class Error(Exception):
     def __init__(self, *args, **kwargs):
         for key, value in kwargs.items():
             if getattr(self, key, object()) is not None:  # pragma: no cover
-                raise TypeError('Invalid argument: {}'.format(key))
+                raise TypeError(f'Invalid argument: {key}')
             setattr(self, key, value)
 
         super().__init__(*args)
@@ -25,7 +25,7 @@ class UserError(Error, ValueError):
     def __str__(self):
         msg = Error.__str__(self)
         for problem in self.problems or ():
-            msg += '\n  - {}'.format(problem)
+            msg += f'\n  - {problem}'
 
         return msg
 
diff --git a/vdirsyncer/http.py b/vdirsyncer/http.py
index 5cb6204..8549216 100644
--- a/vdirsyncer/http.py
+++ b/vdirsyncer/http.py
@@ -7,7 +7,7 @@ from . import DOCS_HOME, exceptions, __version__
 
 
 logger = logging.getLogger(__name__)
-USERAGENT = 'vdirsyncer/{}'.format(__version__)
+USERAGENT = f'vdirsyncer/{__version__}'
 
 
 def _detect_faulty_requests():  # pragma: no cover
@@ -133,7 +133,7 @@ def request(method, url, session=None, latin1_fallback=True,
 
     func = session.request
 
-    logger.debug('{} {}'.format(method, url))
+    logger.debug(f'{method} {url}')
     logger.debug(kwargs.get('headers', {}))
     logger.debug(kwargs.get('data', None))
     logger.debug('Sending request...')
diff --git a/vdirsyncer/metasync.py b/vdirsyncer/metasync.py
index 875f255..82a4556 100644
--- a/vdirsyncer/metasync.py
+++ b/vdirsyncer/metasync.py
@@ -16,12 +16,12 @@ class MetaSyncConflict(MetaSyncError):
 
 def metasync(storage_a, storage_b, status, keys, conflict_resolution=None):
     def _a_to_b():
-        logger.info('Copying {} to {}'.format(key, storage_b))
+        logger.info(f'Copying {key} to {storage_b}')
         storage_b.set_meta(key, a)
         status[key] = a
 
     def _b_to_a():
-        logger.info('Copying {} to {}'.format(key, storage_a))
+        logger.info(f'Copying {key} to {storage_a}')
         storage_a.set_meta(key, b)
         status[key] = b
 
@@ -45,10 +45,10 @@ def metasync(storage_a, storage_b, status, keys, conflict_resolution=None):
         a = storage_a.get_meta(key)
         b = storage_b.get_meta(key)
         s = normalize_meta_value(status.get(key))
-        logger.debug('Key: {}'.format(key))
-        logger.debug('A: {}'.format(a))
-        logger.debug('B: {}'.format(b))
-        logger.debug('S: {}'.format(s))
+        logger.debug(f'Key: {key}')
+        logger.debug(f'A: {a}')
+        logger.debug(f'B: {b}')
+        logger.debug(f'S: {s}')
 
         if a != s and b != s:
             _resolve_conflict()
diff --git a/vdirsyncer/repair.py b/vdirsyncer/repair.py
index 6c8b257..89c2c3a 100644
--- a/vdirsyncer/repair.py
+++ b/vdirsyncer/repair.py
@@ -25,7 +25,7 @@ def repair_storage(storage, repair_unsafe_uid):
                          'The PRODID property may indicate which software '
                          'created this item.'
                          .format(href))
-            logger.error('Item content: {!r}'.format(item.raw))
+            logger.error(f'Item content: {item.raw!r}')
             continue
 
         seen_uids.add(new_item.uid)
diff --git a/vdirsyncer/storage/base.py b/vdirsyncer/storage/base.py
index 7dfcbdd..b78f828 100644
--- a/vdirsyncer/storage/base.py
+++ b/vdirsyncer/storage/base.py
@@ -71,7 +71,7 @@ class Storage(metaclass=StorageMeta):
         self.read_only = bool(read_only)
 
         if collection and instance_name:
-            instance_name = '{}/{}'.format(instance_name, collection)
+            instance_name = f'{instance_name}/{collection}'
         self.instance_name = instance_name
         self.collection = collection
 
diff --git a/vdirsyncer/storage/dav.py b/vdirsyncer/storage/dav.py
index a3becb7..4481e15 100644
--- a/vdirsyncer/storage/dav.py
+++ b/vdirsyncer/storage/dav.py
@@ -34,7 +34,7 @@ del _generate_path_reserved_chars
 def _contains_quoted_reserved_chars(x):
     for y in _path_reserved_chars:
         if y in x:
-            dav_logger.debug('Unsafe character: {!r}'.format(y))
+            dav_logger.debug(f'Unsafe character: {y!r}')
             return True
     return False
 
@@ -52,7 +52,7 @@ def _assert_multistatus_success(r):
         except (ValueError, IndexError):
             continue
         if st < 200 or st >= 400:
-            raise HTTPError('Server error: {}'.format(st))
+            raise HTTPError(f'Server error: {st}')
 
 
 def _normalize_href(base, href):
@@ -78,7 +78,7 @@ def _normalize_href(base, href):
     x = urlparse.quote(x, '/@%:')
 
     if orig_href == x:
-        dav_logger.debug('Already normalized: {!r}'.format(x))
+        dav_logger.debug(f'Already normalized: {x!r}')
     else:
         dav_logger.debug('Normalized URL from {!r} to {!r}'
                          .format(orig_href, x))
@@ -459,7 +459,7 @@ class DAVStorage(Storage):
         for href in hrefs:
             if href != self._normalize_href(href):
                 raise exceptions.NotFoundError(href)
-            href_xml.append('<D:href>{}</D:href>'.format(href))
+            href_xml.append(f'<D:href>{href}</D:href>')
         if not href_xml:
             return ()
 
@@ -591,7 +591,7 @@ class DAVStorage(Storage):
                 props = _merge_xml(props)
 
             if props.find('{DAV:}resourcetype/{DAV:}collection') is not None:
-                dav_logger.debug('Skipping {!r}, is collection.'.format(href))
+                dav_logger.debug(f'Skipping {href!r}, is collection.')
                 continue
 
             etag = getattr(props.find('{DAV:}getetag'), 'text', '')
@@ -641,7 +641,7 @@ class DAVStorage(Storage):
         except KeyError:
             raise exceptions.UnsupportedMetadataError()
 
-        xpath = '{{{}}}{}'.format(namespace, tagname)
+        xpath = f'{{{namespace}}}{tagname}'
         data = '''<?xml version="1.0" encoding="utf-8" ?>
             <D:propfind xmlns:D="DAV:">
                 <D:prop>
@@ -674,7 +674,7 @@ class DAVStorage(Storage):
         except KeyError:
             raise exceptions.UnsupportedMetadataError()
 
-        lxml_selector = '{{{}}}{}'.format(namespace, tagname)
+        lxml_selector = f'{{{namespace}}}{tagname}'
         element = etree.Element(lxml_selector)
         element.text = normalize_meta_value(value)
 
diff --git a/vdirsyncer/storage/etesync.py b/vdirsyncer/storage/etesync.py
index 80339d1..e351d61 100644
--- a/vdirsyncer/storage/etesync.py
+++ b/vdirsyncer/storage/etesync.py
@@ -66,7 +66,7 @@ class _Session:
         key = self._get_key()
         if not key:
             password = click.prompt('Enter key password', hide_input=True)
-            click.echo('Deriving key for {}'.format(self.email))
+            click.echo(f'Deriving key for {self.email}')
             self.etesync.derive_key(password)
             self._set_key(self.etesync.cipher_key)
         else:
@@ -134,7 +134,7 @@ class EtesyncStorage(Storage):
                     **kwargs
                 )
             else:
-                logger.debug('Skipping collection: {!r}'.format(entry))
+                logger.debug(f'Skipping collection: {entry!r}')
 
     @classmethod
     def create_collection(cls, collection, email, secrets_dir, server_url=None,
diff --git a/vdirsyncer/storage/google.py b/vdirsyncer/storage/google.py
index f09ff48..1702f01 100644
--- a/vdirsyncer/storage/google.py
+++ b/vdirsyncer/storage/google.py
@@ -80,7 +80,7 @@ class GoogleSession(dav.DAVSession):
                 # access_type and approval_prompt are Google specific
                 # extra parameters.
                 access_type='offline', approval_prompt='force')
-            click.echo('Opening {} ...'.format(authorization_url))
+            click.echo(f'Opening {authorization_url} ...')
             try:
                 open_graphical_browser(authorization_url)
             except Exception as e:
diff --git a/vdirsyncer/storage/memory.py b/vdirsyncer/storage/memory.py
index 74b58e8..99e533b 100644
--- a/vdirsyncer/storage/memory.py
+++ b/vdirsyncer/storage/memory.py
@@ -6,7 +6,7 @@ from .. import exceptions
 
 
 def _random_string():
-    return '{:.9f}'.format(random.random())
+    return f'{random.random():.9f}'
 
 
 class MemoryStorage(Storage):
diff --git a/vdirsyncer/utils.py b/vdirsyncer/utils.py
index 5559ec3..2737cbe 100644
--- a/vdirsyncer/utils.py
+++ b/vdirsyncer/utils.py
@@ -73,7 +73,7 @@ def get_etag_from_file(f):
     mtime = getattr(stat, 'st_mtime_ns', None)
     if mtime is None:
         mtime = stat.st_mtime
-    return '{:.9f};{}'.format(mtime, stat.st_ino)
+    return f'{mtime:.9f};{stat.st_ino}'
 
 
 def get_storage_init_specs(cls, stop_at=object):
@@ -125,7 +125,7 @@ def checkdir(path, create=False, mode=0o750):
 
     if not os.path.isdir(path):
         if os.path.exists(path):
-            raise OSError('{} is not a directory.'.format(path))
+            raise OSError(f'{path} is not a directory.')
         if create:
             os.makedirs(path, mode)
         else:
@@ -143,7 +143,7 @@ def checkfile(path, create=False):
     checkdir(os.path.dirname(path), create=create)
     if not os.path.isfile(path):
         if os.path.exists(path):
-            raise OSError('{} is not a file.'.format(path))
+            raise OSError(f'{path} is not a file.')
         if create:
             with open(path, 'wb'):
                 pass
diff --git a/vdirsyncer/vobject.py b/vdirsyncer/vobject.py
index 521e97c..33c2d3d 100644
--- a/vdirsyncer/vobject.py
+++ b/vdirsyncer/vobject.py
@@ -205,14 +205,14 @@ def join_collection(items, wrappers=_default_join_wrappers):
 
     if wrapper_type is not None:
         lines = chain(*(
-            ['BEGIN:{}'.format(wrapper_type)],
+            [f'BEGIN:{wrapper_type}'],
             # XXX: wrapper_props is a list of lines (with line-wrapping), so
             # filtering out duplicate lines will almost certainly break
             # multiline-values.  Since the only props we usually need to
             # support are PRODID and VERSION, I don't care.
             uniq(wrapper_props),
             lines,
-            ['END:{}'.format(wrapper_type)]
+            [f'END:{wrapper_type}']
         ))
     return ''.join(line + '\r\n' for line in lines)
 
@@ -299,14 +299,14 @@ class _Component:
             return rv[0]
 
     def dump_lines(self):
-        yield 'BEGIN:{}'.format(self.name)
+        yield f'BEGIN:{self.name}'
         yield from self.props
         for c in self.subcomponents:
             yield from c.dump_lines()
-        yield 'END:{}'.format(self.name)
+        yield f'END:{self.name}'
 
     def __delitem__(self, key):
-        prefix = ('{}:'.format(key), '{};'.format(key))
+        prefix = (f'{key}:', f'{key};')
         new_lines = []
         lineiter = iter(self.props)
         while True:
@@ -329,7 +329,7 @@ class _Component:
         assert isinstance(val, str)
         assert '\n' not in val
         del self[key]
-        line = '{}:{}'.format(key, val)
+        line = f'{key}:{val}'
         self.props.append(line)
 
     def __contains__(self, obj):
@@ -342,8 +342,8 @@ class _Component:
             raise ValueError(obj)
 
     def __getitem__(self, key):
-        prefix_without_params = '{}:'.format(key)
-        prefix_with_params = '{};'.format(key)
+        prefix_without_params = f'{key}:'
+        prefix_with_params = f'{key};'
         iterlines = iter(self.props)
         for line in iterlines:
             if line.startswith(prefix_without_params):