Unsupported URL scheme '(scheme)': (self._notconfigured[scheme])

Raise code

            self._handlers[scheme] = dh
            return dh

    def download_request(self, request, spider):
        scheme = urlparse_cached(request).scheme
        handler = self._get_handler(scheme)
        if not handler:
            raise NotSupported(f"Unsupported URL scheme '{scheme}': {self._notconfigured[scheme]}")
        return handler.download_request(request, spider)

    @defer.inlineCallbacks
    def _close(self, *_a, **_kw):
        for dh in self._handlers.values():
            if hasattr(dh, 'close'):
                yield dh.close()