fix(auth): fall back when certificate callbacks return empty credentials - #18435

fix(auth): fall back when certificate callbacks return empty credentials#18435

Shubham-Padkonde wants to merge 2 commits into

googleapis:maingoogleapis/google-cloud-python:mainfrom

Shubham-Padkonde:fix/auth-empty-certificate-callbackShubham-Padkonde/google-cloud-python:fix/auth-empty-certificate-callbackCopy head branch name to clipboard