Revert "Pin pycparser version."
Revert "Pin pycparser version."

This reverts commit 60ff9b18b3a8bec4b13958b4f15f46815c9aa836.

neiljerram/felix,neiljerram/felix,neiljerram/felix,neiljerram/felix,Metaswitch/calico,Metaswitch/calico