custom error code for not leaving server notices room

synapse/api/errors.py

@@ -53,6 +53,7 @@ class Codes(object):
     INVALID_USERNAME = "M_INVALID_USERNAME"
     SERVER_NOT_TRUSTED = "M_SERVER_NOT_TRUSTED"
     CONSENT_NOT_GIVEN = "M_CONSENT_NOT_GIVEN"
+    CANNOT_LEAVE_SERVER_NOTICE_ROOM = "M_CANNOT_LEAVE_SERVER_NOTICE_ROOM"
 
 
 class CodeMessageException(RuntimeError):

synapse/handlers/room_member.py

@@ -306,6 +306,7 @@ class RoomMemberHandler(object):
                 raise SynapseError(
                     http_client.FORBIDDEN,
                     "You cannot leave this room",
+                    errcode=Codes.CANNOT_LEAVE_SERVER_NOTICE_ROOM,
                 )
 
         if effective_membership_state == Membership.INVITE: