Add an EventValidator. Fix bugs in auth ++ storage

synapse/storage/registration.py

@@ -107,13 +107,17 @@ class RegistrationStore(SQLBaseStore):
             token
         )
 
+    @defer.inlineCallbacks
     def is_server_admin(self, user):
-        return self._simple_select_one_onecol(
+        res = yield self._simple_select_one_onecol(
             table="users",
             keyvalues={"name": user.to_string()},
             retcol="admin",
+            allow_none=True,
         )
 
+        defer.returnValue(res if res else False)
+
     def _query_for_auth(self, txn, token):
         sql = (
             "SELECT users.name, users.admin, access_tokens.device_id "