Update noxfile.py

Author: abbrowne126

noxfile.py

@@ -117,7 +117,7 @@ def mypy(session):
     # TODO: Only check the hand-written layer, the generated code does not pass
     # mypy checks yet.
     # https://github.com/googleapis/gapic-generator-python/issues/1092
-    session.run("mypy", "-p", "google.cloud", "--exclude", "google/pubsub_v1")
+    session.run("mypy", "-i", "-p", "google.cloud", "--exclude", "'google/pubsub_v1/'")
 
 
 @nox.session(python=DEFAULT_PYTHON_VERSION)