'get_delegation_token(user) -> Delegation token'

def get_delegation_token(self, renewer):

    if self._security_enabled:
        self.get_home_dir()
    params = self._getparams()
    params['op'] = 'GETDELEGATIONTOKEN'
    params['renewer'] = renewer
    res = self._root.get(params=params)
    return res['Token']['urlString']
