To reproduce the bug, build the master branch of Python and then run:

./python -m venv venv
./venv/bin/python -m pip install -U coverage

Or just:

$ ./venv/bin/python -c 'from distutils import sysconfig; print(sysconfig.get_python_inc())'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/haypo/prog/python/master/Lib/distutils/sysconfig.py", line 100, in get_python_inc
    incdir = os.path.join(_sys_home, get_config_var('AST_H_DIR'))
  File "/home/haypo/prog/python/master/Lib/posixpath.py", line 92, in join
    genericpath._check_arg_types('join', a, *p)
  File "/home/haypo/prog/python/master/Lib/genericpath.py", line 149, in _check_arg_types
    (funcname, s.__class__.__name__)) from None
TypeError: join() argument must be str or bytes, not 'NoneType'