Fix annotation and usage of get_rfcomm_channel

The expected type is actually int and we have to make sure that it is not None.

blueman/services/meta/SerialService.py

@@ -53,7 +53,10 @@ def connect(
         reply_handler: Optional[Callable[[str], None]] = None,
         error_handler: Optional[Callable[[RFCOMMError], None]] = None
     ) -> bool:
-        channel = get_rfcomm_channel(self.short_uuid, self.device['Address'])
+        # We expect this service to have a reserved UUID
+        uuid = self.short_uuid
+        assert uuid
+        channel = get_rfcomm_channel(uuid, self.device['Address'])
         if channel is None or channel == 0:
             error = RFCOMMError("Failed to get rfcomm channel")
             if error_handler:

stubs/_blueman.pyi

@@ -53,6 +53,6 @@ def create_rfcomm_device(local_address: str, remote_address: str, channel: int)
 def destroy_bridge(name: str = "pan1") -> None: ...
 def device_info(hci_name: str = "hci0") -> _HciInfo: ...
 def page_timeout(hci_name: str = "hci0") -> float: ...
-def get_rfcomm_channel(uuid: str, bdaddr: str) -> Optional[int]: ...
+def get_rfcomm_channel(uuid: int, bdaddr: str) -> Optional[int]: ...
 def release_rfcomm_device(id: int) -> int: ...
 def rfcomm_list() -> List[_RfcommDev]: ...