It seems like the SDK being used does not have currently supported SSL certificates bundled with it. If you have an older version of the stand-alone SDK, the bundled certs may be outdated. If you have the newest version of the standalone SDK, the certs may still not have been updated. Having just tested the
original App Engine SDK for Python myself (version 1.9.52) however, I can confirm that I was able to deploy my test application successfully without SSL handshake errors.
If you also have the newest version and still get this error when using the CLI appcfg.py update <your-app.yaml>, I would recommend filing a new issue on the Issue Tracker. If you have an earlier version and want to continue using the stand-alone App Engine SDK, I'd recommend downloading the newest version which is currently 1.9.52.
If you're not particularly attached to the stand-alone SDK, I strongly recommend switching to the
Cloud SDK as this is where much of
Google's energy is spent for deployment tools. It is a much more robust tool set and includes commands for almost all Google Cloud products so quite versatile.