'Verify that no_auth removes existing authentication.'

def test_no_auth(self):

    s = self.build_session()
    s.basic_auth('user', 'password')
    s.headers['Authorization'] = 'token    foobarbogus'
    with s.no_auth():
        assert ('Authentication' not in s.headers)
        assert (s.auth is None)
    assert (s.headers['Authorization'] == 'token    foobarbogus')
    assert (s.auth == ('user', 'password'))
