Yes, unfortunately Google never created an official API for Keep so the underlying library has to cheat as if it is an Android app. This ‘bad authentication’ error shows up mostly on Windows OSs due to a TLS issue. The author of the library has hopefully fixed the problem very recently. If you run - pip install gkeepapi==0.13.4 and try the test again it may work.
For reference - if you do a ‘pip list’ the key libraries should be at:
gkeepapi 0.13.4
gpsoauth 0.4.1
requests 2.23.0
urllib3 1.25.11
If you have newer versions of requests and urllib3 then that’s what is causing the ‘bad authentication’ error.