Extended Description

Since r361998 lit test suite (i.e. tests of lit itself) no longer work when run standalone. This is unfortunate for us since we package lit separately, and do not wish to have to configure whole LLVM in order to test it.

$ lit -v tests
lit: /usr/lib/python3.7/site-packages/lit/TestingConfig.py:102: fatal: unable to parse config file '/home/mgorny/git/llvm-project/llvm/utils/lit/tests/lit.cfg', traceback: Traceback (most recent call last):
File "/usr/lib/python3.7/site-packages/lit/TestingConfig.py", line 89, in load_from_path
exec(compile(data, path, 'exec'), cfg_globals, None)
File "/home/mgorny/git/llvm-project/llvm/utils/lit/tests/lit.cfg", line 38, in
llvm_config.with_environment('PYTHONPATH', lit_path, append_path=True)
AttributeError: 'NoneType' object has no attribute 'with_environment'

I've pointed the issue out in https://reviews.llvm.org/D61798 but received no reply.