hg: use localrepo.instance instead of invoking localrepository directly The instance method has been available for very long time and does almost the same thing. Also, for Mercurial 4.8, the create functionality is only available on the instance factory.

# requirements.txt file for use as "pip install -r requirements.txt" as a
# readthedocs compatible alternative to "pip install -e ." which is a working
# alternative to "setup.py develop" which doesn't work with Mercurial 3.7
.