praekelt/vumi — pull request #688 by smn (2013-12-23 20:58:34+00:00)
Title: ConfigClassName field for vumi.config needs to allow for zope.interface checks.

If given an `implements` keyword argument the `ConfigClassName` should check whether the class pointed at [implements](http://docs.zope.org/zope.interface/api.html#ISpecification.implementedBy) a specific `zope.interface.Interface`.

This was suggested by @hodgestar in the review of #677