Change the Python startup approach.

Although commit 163a25b was a good first step, still getting Travis CI
broken pipe errors. when running tests, any module that required
enhance-body.rkt was causing the Pygments process to launch -- even
though there was no call to `pygmentize`. Why? Because the exit handler
was calling `stop`, which in turn called `running?`, which ironically
ended up _starting_ the process. Gah. TL;DR `running?` was doing too
much work. Refactored.