'Remove a compute host from an aggregate.
The counter action to this is :func:`add_to_aggregate`
:param nova.context.RequestContext context:
The security context.
:param nova.objects.aggregate.Aggregate aggregate:
The aggregate which should remove the given `host`
:param str host:
The name of the host to remove from the given `aggregate`.
:param dict kwargs:
A free-form thingy...
:return: None'

def remove_from_aggregate(self, context, aggregate, host, **kwargs):

    raise NotImplementedError()
