Fix error from new flake8 version. (#6309)
Fix error from new flake8 version. (#6309)

Presumably, anyway, as the line of code in question hasn't changed for
almost a year.
dhermes/google-cloud-python,jonparrott/gcloud-python,tswast/google-cloud-python,GoogleCloudPlatform/gcloud-python,dhermes/google-cloud-python,tswast/google-cloud-python,dhermes/google-cloud-python,jonparrott/google-cloud-python,GoogleCloudPlatform/gcloud-python,tseaver/google-cloud-python,tseaver/google-cloud-python,googleapis/google-cloud-python,jonparrott/google-cloud-python,dhermes/gcloud-python,jonparrott/gcloud-python,tswast/google-cloud-python,dhermes/gcloud-python,tseaver/google-cloud-python,googleapis/google-cloud-python