Protect against broken packages in python env
Protect against broken packages in python env

As seen in https://groups.google.com/forum/#!msg/octoprint/DyXdqhR0U7c/kKMUsMmIBgAJ
a broken entry_points.txt in some arbitrary Python package installed in
the same python envrionment as OctoPrint can make our whole plugin
detection fail and hence interrupt regular server startup.

This adds better protection against such cases.

foosel/OctoPrint,Jaesin/OctoPrint,Jaesin/OctoPrint,foosel/OctoPrint,foosel/OctoPrint,Jaesin/OctoPrint,foosel/OctoPrint,Jaesin/OctoPrint