Mailing list EmailProperty should be StringProperty instead, so that it is
possible, for example, to supply a Google Group URL for sign-up purposes.
Patch by: Todd Larsen
Review by: to-be-reviewed
"""Multi-consumer multi-producer dispatching mechanism
Originally based on pydispatch (BSD) http://pypi.python.org/pypi/PyDispatcher/2.0.1
See license.txt for original license.
Heavily modified for Django's purposes.
"""
from django.dispatch.dispatcher import Signal