'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.'

def add_email_grant(self, permission, email_address):

    acl = self.get_acl()
    acl.add_email_grant(permission, email_address)
    self.set_acl(acl)
