Enable mypy option --disallow-untyped-calls (#611)

Co-authored-by: Tom Christie <tom@tomchristie.com>

setup.cfg

@@ -9,6 +9,7 @@ ignore_missing_imports = True
 no_implicit_optional = True
 show_error_codes = True
 warn_unused_ignores = True
+disallow_untyped_calls = True
 
 [mypy-tests.*]
 disallow_untyped_defs = False

tests/concurrency.py

@@ -10,7 +10,7 @@
 """
 import threading
 from types import TracebackType
-from typing import List, Optional, Type
+from typing import Any, Callable, List, Optional, Type
 
 
 class Nursery:
@@ -31,7 +31,7 @@ def __exit__(
         for thread in self._threads:
             thread.join()
 
-    def start_soon(self, func, *args):
+    def start_soon(self, func: Callable[..., object], *args: Any):
         thread = threading.Thread(target=func, args=args)
         self._threads.append(thread)