Fix base-client used wrongly (frequenz-floss#108)

Author: Marenz

RELEASE_NOTES.md

@@ -1,7 +1,5 @@
 # Frequenz Dispatch Client Library Release Notes
 
-## New Features
+## Bug Fixes
 
-* Update BaseApiClient to get the http2 keepalive feature.
-* Some Methods from the high-level API have been moved to this repo: The dispatch class now offers: `until`, `started`, `next_run` and `next_run_after`.
-* Add `start_immediately` support to the `create` method. You can now specify "NOW" as the start time to trigger immediate dispatch. Note: While the dispatch CLI previously allowed this by converting "NOW" to a timestamp client-side before sending it to the server, this functionality is now supported directly on the server side!
+* The client was broken due to wrong usage of the new BaseClient API.

src/frequenz/client/dispatch/_client.py

@@ -93,10 +93,11 @@ def __init__(
         self._setup_stub()
 
     def _setup_stub(self) -> None:
-        self._stub = cast(
-            dispatch_pb2_grpc.MicrogridDispatchServiceAsyncStub,
-            dispatch_pb2_grpc.MicrogridDispatchServiceStub(self.channel),
-        )
+        stub = dispatch_pb2_grpc.MicrogridDispatchServiceStub(self.channel)
+        # We need the type: ignore here because the generated async stub only lives in
+        # the .pyi file (the interpreter doesn't know anything about it) so we can't use
+        # a proper `cast()`, we can only use the async stub as a type hint.
+        self._stub: dispatch_pb2_grpc.MicrogridDispatchServiceAsyncStub = stub  # type: ignore
 
     @property
     def stub(self) -> dispatch_pb2_grpc.MicrogridDispatchServiceAsyncStub: