Incorrect handling of user+password authentication

[orwonthe]

When executing rdm pull without access token the user is prompted for github username and password. This interaction works fine except that the resulting history.yml file starts with:
GitHub username: change_requests:
instead of the expected:
change_requests:
This causes later commands to fail with errors like:
yaml.scanner.ScannerError: mapping values are not allowed here in "<unicode string>", line 1, column 33: GitHub username: change_requests:
The work around, until this is fixed, is to edit out the leading GitHub username: