'Convenience method that provides a quick way to add an email grant
to a bucket. 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 GCS.
:type permission: string
:param permission: The permission being granted. Should be one of:
(READ, WRITE, FULL_CONTROL).
:type email_address: string
:param email_address: The email address associated with the GS
account your are granting the permission to.
:type recursive: bool
:param recursive: A boolean value to controls whether the call
will apply the grant to all keys within the bucket
or not.  The default value is False.  By passing a
True value, the call will iterate through all keys
in the bucket and apply the same grant to each key.
CAUTION: If you have a lot of keys, this could take
a long time!'

def add_email_grant(self, permission, email_address, recursive=False, headers=None):

    if (permission not in GSPermissions):
        raise self.connection.provider.storage_permissions_error(('Unknown    Permission:    %s' % permission))
    acl = self.get_acl(headers=headers)
    acl.add_email_grant(permission, email_address)
    self.set_acl(acl, headers=headers)
    if recursive:
        for key in self:
            key.add_email_grant(permission, email_address, headers=headers)
