Get the email address of the project's GCS service account

        :type project: str
        :param project:
            (Optional) Project ID to use for retreiving GCS service account
            email address.  Defaults to the client's project.

        :rtype: str
        :returns: service account email address

def get_service_account_email(self, project=None):
        """Get the email address of the project's GCS service account

        :type project: str
        :param project:
            (Optional) Project ID to use for retreiving GCS service account
            email address.  Defaults to the client's project.

        :rtype: str
        :returns: service account email address
        """
        if project is None:
            project = self.project
        path = "/projects/%s/serviceAccount" % (project,)
        api_response = self._base_connection.api_request(method="GET", path=path)
        return api_response["email_address"]