def _include_environment_variables(self, program, executor_vars):
        """Define environment variables."""
        env_vars = {
            'RESOLWE_HOST_URL': self.settings_actual.get('RESOLWE_HOST_URL', 'localhost'),
        }

        set_env = self.settings_actual.get('FLOW_EXECUTOR', {}).get('SET_ENV', {})
        env_vars.update(executor_vars)
        env_vars.update(set_env)

        export_commands = ['export {}={}'.format(key, shlex.quote(value)) for key, value in env_vars.items()]
        return os.linesep.join(export_commands) + os.linesep + program
Define environment variables.