code: def get_service_env_value(self, key):
          
          service_key = predix.config.get_env_key(self, key)
          value = os.environ[service_key]
          if not value:
              raise ValueError("%s env unset" % key)
          return value
docs: Get a env variable as defined by the service admin
          :param key: the base of the key to use
          :return: the env if it exists