routing: Fix breakages with routing on some versions of Python. Finally figured what happened with change 6baa94da8b16 (this is a Mercurial hash by the way if you're looking at the Git mirror). Between Python 3.6 and 3.7 there was a change where the percent sign ('%') went from being escaped by `re.escape` to _not_ being escaped. So now we need to use different regex patterns dependin on the Python version, yay.

include CHANGELOG.rst
include INSTALL.rst
include LICENSE.rst
include README.rst

include pytest.ini
include setup.cfg
include requirements.txt
include dev-requirements.txt

recursive-include piecrust *
recursive-include tests *

global-exclude *.py[cdo] __pycache__ *.so
global-exclude .DS_Store Thumbs.db Desktop.ini
global-exclude *.swp *~ *.bak