[refactor] make get_total_storage() return a deferred

src/leap/soledad/server/interfaces.py

@@ -143,6 +143,10 @@ class IBlobsBackend(Interface):
 
         :return: The size in units of 1024 bytes.
         :rtype: int
+
+        :return: A deferred that fires with the amount of storage used in units
+            of 1024 bytes.
+        :rtype: twisted.internet.defer.Deferred
         """
 
     def get_tag(user, blob_id, namespace=''):

tests/blobs/test_fs_backend.py

@@ -96,7 +96,7 @@ class FilesystemBackendTestCase(unittest.TestCase):
     def test_write_cannot_exceed_quota(self, isfile):
         isfile.return_value = False
         backend = _blobs.FilesystemBlobsBackend(blobs_path=self.tempdir)
-        backend.get_total_storage = lambda x: 100
+        backend.get_total_storage = lambda x: defer.succeed(100)
         backend.quota = 90
         with pytest.raises(_blobs.QuotaExceeded):
             fd = Mock()