'Call ``PATCH /credentials/{credential_id}``.'

def test_update_credential(self):

    ref = unit.new_credential_ref(user_id=self.user['id'], project_id=self.project_id)
    del ref['id']
    r = self.patch(('/credentials/%(credential_id)s' % {'credential_id': self.credential['id']}), body={'credential': ref})
    self.assertValidCredentialResponse(r, ref)
