Upgrade to Python 3 and use PAT not password

[earlephilhower]

Need to change the uploader to use PAT and Python 3 (Python2 EOL on 1/1/20):

You recently used a password to access an endpoint through the GitHub API using PyGithub/Python. We will deprecate basic authentication using password to this endpoint soon:

We recommend using a personal access token (PAT) with the appropriate scope to access this endpoint instead. Visit https://github.com/settings/tokens for more information.