A working post_save signal handler

models.py

class Repository(BaremetalModel):
    account = models.ForeignKey('Account')
    url = GitURIField()

    def __unicode__(self):
        return unicode(self.url)

    def do_something(self):
        pass

    @classmethod
    def post_save(cls, sender, instance, **kwargs):
        instance.do_something()
models.signals.post_save.connect(Repository.post_save, sender=Repository)