Nicer error message for InvalidResponse

See #448

tests/cli/test_utils.py

@@ -10,7 +10,9 @@ from hypothesis.strategies import (
     text
 )
 
-from vdirsyncer.cli.utils import coerce_native
+
+from vdirsyncer import exceptions
+from vdirsyncer.cli.utils import coerce_native, handle_cli_error
 
 
 @given(one_of(
@@ -24,3 +26,14 @@ from vdirsyncer.cli.utils import coerce_native
 ))
 def test_coerce_native_fuzzing(s):
     coerce_native(s)
+
+
+def test_handle_cli_error(capsys):
+    try:
+        raise exceptions.InvalidResponse('ayy lmao')
+    except:
+        handle_cli_error()
+
+    out, err = capsys.readouterr()
+    assert 'returned something vdirsyncer doesn\'t understand' in err
+    assert 'ayy lmao' in err

vdirsyncer/__init__.py

@@ -6,6 +6,7 @@ vdirsyncer is a synchronization tool for vdir. See the README for more details.
 from __future__ import print_function
 
 PROJECT_HOME = 'https://github.com/pimutils/vdirsyncer'
+BUGTRACKER_HOME = PROJECT_HOME + '/issues'
 DOCS_HOME = 'https://vdirsyncer.readthedocs.io/en/stable'
 
 try:

vdirsyncer/cli/utils.py

@@ -16,7 +16,7 @@ import click
 import click_threading
 
 from . import cli_logger
-from .. import DOCS_HOME, exceptions
+from .. import BUGTRACKER_HOME, DOCS_HOME, exceptions
 from ..sync import IdentConflict, StorageEmpty, SyncConflict
 from ..utils import expand_path, get_storage_init_args
 from ..utils.compat import to_native
@@ -128,6 +128,15 @@ def handle_cli_error(status_name=None):
             'configuration file and make sure you\'ve typed the pair name '
             'correctly'.format(pair_name=e.pair_name)
         )
+    except exceptions.InvalidResponse as e:
+        cli_logger.error(
+            'The server returned something vdirsyncer doesn\'t understand. '
+            'Error message: {!r}\n'
+            'While this is most likely a serverside problem, the vdirsyncer '
+            'devs are generally interested in such bugs. Please report it in '
+            'the issue tracker at {}'
+            .format(e, BUGTRACKER_HOME)
+        )
     except Exception as e:
         if status_name:
             msg = 'Unhandled exception occured for {}.'.format(