git: fix upload-pack content-type with py3 It is checked earlier that git_command is one of two string constants, and with py3, things are much simpler and we don't have to consider string coersion. Reported and debugged by Valentin.

# 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
.