code: def add_email_grant(self, permission, email_address):
          
          acl = self.get_acl()
          acl.add_email_grant(permission, email_address)
          self.set_acl(acl)
docs: Convenience method that provides a quick way to add an email 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
                                account to which you are granting the permission.