Add smarter auth import to deal with race conditions by multi sessions

- Add a retry mechanism (up to three times)
- Narrow the window in which export+import executes
- Remove a line of duplicated code

Fixes #299

pyrogram/client/client.py

@@ -45,7 +45,7 @@ from pyrogram.errors import (
     PhoneCodeExpired, PhoneCodeEmpty, SessionPasswordNeeded,
     PasswordHashInvalid, FloodWait, PeerIdInvalid, FirstnameInvalid, PhoneNumberBanned,
     VolumeLocNotFound, UserMigrate, ChannelPrivate, PhoneNumberOccupied,
-    PasswordRecoveryNa, PasswordEmpty
+    PasswordRecoveryNa, PasswordEmpty, AuthBytesInvalid
 )
 from pyrogram.session import Auth, Session
 from .ext import utils, Syncer, BaseClient, Dispatcher
@@ -1720,27 +1720,32 @@ class Client(Methods, BaseClient):
 
             if session is None:
                 if dc_id != self.storage.dc_id:
+                    session = Session(self, dc_id, Auth(self, dc_id).create(), is_media=True)
+                    session.start()
+
+                    for _ in range(3):
                         exported_auth = self.send(
                             functions.auth.ExportAuthorization(
                                 dc_id=dc_id
                             )
                         )
 
-                    session = Session(self, dc_id, Auth(self, dc_id).create(), is_media=True)
+                        try:
-
-                    session.start()
-
-                    self.media_sessions[dc_id] = session
-
                             session.send(
                                 functions.auth.ImportAuthorization(
                                     id=exported_auth.id,
                                     bytes=exported_auth.bytes
                                 )
                             )
+                        except AuthBytesInvalid:
+                            continue
+                        else:
+                            break
+                    else:
+                        session.stop()
+                        raise AuthBytesInvalid
                 else:
                     session = Session(self, dc_id, self.storage.auth_key, is_media=True)
-
                     session.start()
 
                 self.media_sessions[dc_id] = session