gistfile1.py

def wrap(app):

    def middleware(env, start_response):
        path = env['PATH_INFO']
        is_forwarded = env['HTTP_X_FORWARDED_FOR']:
        if is_forwarded and path == '/v1/health':
            return start_response('200 OK', [])
        return app(env, start_response)

    return middleware

L5 should be:

is_forwarded = env.get('HTTP_X_FORWARDED_FOR') is not None