There's a test in test_config.py that essentially expects $HOME to be equal to ~$USER. This is not the case in certain build environments (e.g. sbuild for Debian/Ubuntu, which explicitly sets $HOME to a non-existent directory). I have changed the test to check against $HOME instead, which may be pointless but I couldn't come up with anything more reasonable.
Note too that the tests essentially require $HOME exists, otherwise the test suite crashes. Maybe that's also a bug.