'Delete a user\'s access/secret pair.
Used to revoke a user\'s access/secret pair
:param user_id: id of user
:param credential_id: access key for credentials
:returns: bool: success'

def delete_credential(self, user_id, credential_id):

    self.identity_api.get_user(user_id)
    self._get_credentials(credential_id)
    ec2_credential_id = utils.hash_access_key(credential_id)
    return self.credential_api.delete_credential(ec2_credential_id)
