Add create_requester function

Wrap the `Requester` constructor with a function which provides sensible
defaults, and use it throughout

synapse/handlers/_base.py

@@ -13,14 +13,14 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+import logging
+
 from twisted.internet import defer
 
-from synapse.api.errors import LimitExceededError
+import synapse.types
 from synapse.api.constants import Membership, EventTypes
-from synapse.types import UserID, Requester
-
-
-import logging
+from synapse.api.errors import LimitExceededError
+from synapse.types import UserID
 
 
 logger = logging.getLogger(__name__)
@@ -124,7 +124,8 @@ class BaseHandler(object):
                 # and having homeservers have their own users leave keeps more
                 # of that decision-making and control local to the guest-having
                 # homeserver.
-                requester = Requester(target_user, "", True)
+                requester = synapse.types.create_requester(
+                    target_user, is_guest=True)
                 handler = self.hs.get_handlers().room_member_handler
                 yield handler.update_membership(
                     requester,