fix flake8 issues

Author: jensbjorgensen

tests/test_base.py

@@ -941,7 +941,7 @@ def test_loop_call_later_handle_when_after_fired(self):
     def test_loop_call_later_0_returns_timer_handle(self):
         cb = lambda: False  # NoQA
         handle = self.loop.call_later(0, cb)
-        handle.when() # undesired behavior: handle is a Handle instead of TimerHandle
+        handle.when()
         handle.cancel()