ZO-4267: extend mock connector to fullfil locking contract

core/src/zeit/connector/mock.py

@@ -14,7 +14,13 @@
 import zope.event
 
 from zeit.connector.connector import CannonicalId
-from zeit.connector.interfaces import ID_NAMESPACE, UUID_PROPERTY, CopyError, MoveError
+from zeit.connector.interfaces import (
+    ID_NAMESPACE,
+    UUID_PROPERTY,
+    CopyError,
+    LockingError,
+    MoveError,
+)
 import zeit.connector.cache
 import zeit.connector.dav.interfaces
 import zeit.connector.filesystem
@@ -229,6 +235,8 @@ def changeProperties(self, id, properties):
     def lock(self, id, principal, until):
         """Lock resource for principal until a given datetime."""
         id = self._get_cannonical_id(id)
+        if id in self._locked:
+            raise LockingError('Resource is already locked by another principal')
         self._locked[id] = (principal, until, True)
 
     def unlock(self, id, locktoken=None):