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Hello! 

Before Newton release, I just used full module path in nova.conf to plugin. But now blueprints suggest to use built-in drivers via entry points from `nova.scheduler` namespace. 

**How I should plug 3rd-party, not built-in  drivers?** 

I actually tried to add entry points manually to e.g. `/usr/lib/python2.7/site-packages/nova-13.1.0-py2.7.egg-info/entry_points.txt`, and it works, but it doesn't look like correct way.