spereverde/plone.portlet.static — comment on commit f763a8e6420474c09f22d07b9373f72ef10b0673
File: plone/portlet/static/static.py line 108
By gotcha:

In my opinion, this should be AND not OR.

IOW, I would concatenate the custom class to the generated class.

This way, designers will still be able to,style based on both properties.