Fix #2 and #3; improve debugging a bit

[nickmarden]

This was a small basket of fixes I needed to make to enable migration in an enterprise scenario:

• I don't have (local CLI) Github login auth for the repos being transferred; I only have a token
• I am moving repos into a nested project structure in Gitlab. The code previously expected a flat namespace name with no /
• I want to be able to specify the visibility of the newly-created project in Gitlab
• I needed better debugging help to see what was going wrong during my debugging
• Various other bug fixes that arose from running the code under a more recent Python 3.x version