exceptions: Move InvitationError to zerver/lib/exceptions.

zerver/lib/exceptions.py

@@ -1,5 +1,5 @@
 from enum import Enum
-from typing import Any, Dict, List, NoReturn, Optional, Type, TypeVar
+from typing import Any, Dict, List, NoReturn, Optional, Tuple, Type, TypeVar
 
 from django.utils.translation import gettext as _
 
@@ -358,3 +358,15 @@ class InvalidSubdomainError(JsonableError):
 class ZephyrMessageAlreadySentException(Exception):
     def __init__(self, message_id: int) -> None:
         self.message_id = message_id
+
+
+class InvitationError(JsonableError):
+    code = ErrorCode.INVITATION_FAILED
+    data_fields = ["errors", "sent_invitations"]
+
+    def __init__(
+        self, msg: str, errors: List[Tuple[str, str, bool]], sent_invitations: bool
+    ) -> None:
+        self._msg: str = msg
+        self.errors: List[Tuple[str, str, bool]] = errors
+        self.sent_invitations: bool = sent_invitations