Support exclusive conversations by default

telethon/errors/__init__.py

@@ -8,7 +8,8 @@ from threading import Thread
 
 from .common import (
     ReadCancelledError, TypeNotFoundError, InvalidChecksumError,
-    InvalidBufferError, SecurityError, CdnFileTamperedError, MultiError
+    InvalidBufferError, SecurityError, CdnFileTamperedError,
+    AlreadyInConversationError, MultiError
 )
 
 # This imports the base errors too, as they're imported there

telethon/errors/common.py

@@ -79,6 +79,17 @@ class CdnFileTamperedError(SecurityError):
         )
 
 
+class AlreadyInConversationError(Exception):
+    """
+    Occurs when another exclusive conversation is opened in the same chat.
+    """
+    def __init__(self):
+        super().__init__(
+            'Cannot open exclusive conversation in a '
+            'chat that already has one open conversation'
+        )
+
+
 class MultiError(Exception):
     """Exception container for multiple `TLRequest`'s."""