Re-enable lint for tests, remove usage of pylint (#4921)

Author: Jon Wayne Parrott

packages/google-cloud-core/nox.py

@@ -79,8 +79,7 @@ def lint(session):
     serious code quality issues.
     """
     session.interpreter = 'python3.6'
-    session.install(
-        'flake8', 'flake8-import-order', *LOCAL_DEPS)
+    session.install('flake8', 'flake8-import-order')
     session.install('.')
     session.run('flake8', 'google', 'tests')