Code review comment for lp:~lvh/divmod.org/modernize-axiom-packaging

I've noticed another issue with switching away from epsilon.setuphelper; it has a regeneratePluginCache hook to regenerate the Twisted plugin cache (actually, it looks for any directory of the form foo/plugins/ where foo/plugins/__init__.py does not exist). The new setup.py does not have this functionality; on the other hand, after reading https://twistedmatrix.com/trac/ticket/2410 I start to wonder if this functionality shouldn't just be dropped after all.