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

def test_update_credential_to_ec2_missing_project_id(self):

    ref = unit.new_credential_ref(user_id=self.user['id'])
    r = self.post('/credentials', body={'credential': ref})
    self.assertValidCredentialResponse(r, ref)
    credential_id = r.result.get('credential')['id']
    update_ref = {'type': 'ec2'}
    self.patch(('/credentials/%(credential_id)s' % {'credential_id': credential_id}), body={'credential': update_ref}, expected_status=http_client.BAD_REQUEST)
