'Cleans up a slug by removing slug separator characters that occur at
the beginning or end of a slug.
If an alternate separator is used, it will also replace any instances
of the default \'-\' separator with the new separator.'

def _slug_strip(self, value):

    re_sep = ('(?:-|%s)' % re.escape(self.separator))
    value = re.sub(('%s+' % re_sep), self.separator, value)
    return re.sub(('^%s+|%s+$' % (re_sep, re_sep)), '', value)
