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.

import os
from invoke import task, run


@task
def genmessages(ctx):
    root_dir = 'garcon/messages'
    out_dir = 'piecrust/resources/messages'
    run('python chef.py --root %s bake -o %s' % (root_dir, out_dir))
    os.unlink('piecrust/resources/messages/index.html')