middleware: drop fix_PATH Back out ccbdff90e5a0. That seemed like an odd hack. In order to work properly, it should not only be applied for protocol access middleware, but also for web UI and for commands. So evidently, it is not really necessary. The problem it describes is fixed much better in 5e501b6ee639 by setting the right python executable in the hook scripts, further improved in 1bafb2d07709 and 6df08d78f8e7 to *actually* use the right python executable.

# 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
.