def assertListEq(self, l1, l2, ignore):
        ''' succeed iff {l1} - {ignore} == {l2} - {ignore} '''
        missing = (set(l1) ^ set(l2)) - set(ignore)
        if missing:
            print >>sys.stderr, "l1=%r\nl2=%r\nignore=%r" % (l1, l2, ignore)
            self.fail("%r missing" % missing.pop())