Convenience method that provides a quick way to add an email group
        grant to a key. This method retrieves the current ACL, creates a new
        grant based on the parameters passed in, adds that grant to the ACL and
        then PUT's the new ACL back to GS.

        :type permission: string
        :param permission: The permission being granted. Should be one of:
            READ|FULL_CONTROL
            See http://code.google.com/apis/storage/docs/developer-guide.html#authorization
            for more details on permissions.

        :type email_address: string
        :param email_address: The email address associated with the Google
            Group to which you are granting the permission.

def add_group_email_grant(self, permission, email_address, headers=None):
        """
        Convenience method that provides a quick way to add an email group
        grant to a key. This method retrieves the current ACL, creates a new
        grant based on the parameters passed in, adds that grant to the ACL and
        then PUT's the new ACL back to GS.

        :type permission: string
        :param permission: The permission being granted. Should be one of:
            READ|FULL_CONTROL
            See http://code.google.com/apis/storage/docs/developer-guide.html#authorization
            for more details on permissions.

        :type email_address: string
        :param email_address: The email address associated with the Google
            Group to which you are granting the permission.
        """
        acl = self.get_acl(headers=headers)
        acl.add_group_email_grant(permission, email_address)
        self.set_acl(acl, headers=headers)