Fix missing XML header, see #688

CHANGELOG.rst

@@ -9,6 +9,12 @@ Package maintainers and users who have to manually update their installation
 may want to subscribe to `GitHub's tag feed
 <https://github.com/pimutils/vdirsyncer/tags.atom>`_.
 
+Version 0.17.0
+==============
+
+- Fix bug where collection discovery under DAV-storages would produce invalid
+  XML. See :gh:`688`.
+
 Version 0.16.3
 ==============
 

vdirsyncer/storage/dav.py

@@ -146,7 +146,7 @@ class Discover(object):
     _homeset_xml = None
     _homeset_tag = None
     _well_known_uri = None
-    _collection_xml = b"""
+    _collection_xml = b"""<?xml version="1.0" encoding="utf-8" ?>
     <d:propfind xmlns:d="DAV:">
         <d:prop>
             <d:resourcetype />