from http.server import SimpleHTTPRequestHandler, ThreadingHTTPServer

class serveWithHeaders(SimpleHTTPRequestHandler):

    def end_headers(self):
        self.addHeaders()

        SimpleHTTPRequestHandler.end_headers(self)

    def addHeaders(self):
        self.send_header('Permissions-Policy', 'fullscreen=*')           

httpd = ThreadingHTTPServer( ('', 8000), serveWithHeaders)

httpd.serve_forever()