Fix lint warning

Doug Greiman · Doug Greiman · commit d722f0053e59 · 2017-06-26T11:58:19.000-07:00
diff --git a/scripts/gen_dockerfile_test.py b/scripts/gen_dockerfile_test.py
@@ -218,7 +218,8 @@ def mock_error(*args):
         """Prevent argparse from calling sys.exit()"""
         raise AssertionError(*args)
 
-    with unittest.mock.patch.object(
-        argparse.ArgumentParser, 'error', mock_error):
+    error_patch = unittest.mock.patch.object(
+        argparse.ArgumentParser, 'error', mock_error)
+    with error_patch:
         with pytest.raises(AssertionError):
             gen_dockerfile.parse_args(argv)
