'Ensure params are only supplied once'

def test_duplicate_params(self):

    v = RequestValidator()
    e = BaseEndpoint(v)
    self.assertRaises(errors.InvalidRequestError, e._create_request, u'https://a.b/?oauth_version=a&oauth_version=b', u'GET', None, URLENCODED)
    self.assertRaises(errors.InvalidRequestError, e._create_request, u'https://a.b/', u'GET', u'oauth_version=a&oauth_version=b', URLENCODED)
