chore(storage): fix lint error in _signing.py module (#140)
chore(storage): fix lint error in _signing.py module (#140)

Fixes #139 

This PR fixes a lint error that recently started occurring on master out of the blue.
### How to verify

Run the lint check on master:

    $ nox -f noxfile.py -s lint


googleapis/python-storage,googleapis/python-storage