Explicitly list files for mypy

Author: davidbrochart

tox.ini

@@ -18,7 +18,7 @@ commands = flake8 nbclient --count --ignore=E203,E731,F811,W503 --max-complexity
 [testenv:mypy]
 skip_install = true
 deps = mypy
-commands = mypy nbclient/*.py
+commands = mypy nbclient/client.py nbclient/exceptions.py nbclient/__init__.py nbclient/jsonutil.py nbclient/output_widget.py nbclient/util.py nbclient/_version.py
 
 # Manifest
 [testenv:manifest]