riotCode

I got this error from the Media imports, I corrected it by adapting fetch_remote_file() method on wordpress-importer.php:981 to use the WP_Http class:

	function fetch_remote_file( $url, $post ) {
		// extract the file name and extension from the url
		$file_name = basename( $url );

		// get placeholder file in the upload dir with a unique, sanitized filename
		$upload = wp_upload_bits( $file_name, 0, '', $post['upload_date'] );
		if ( $upload['error'] )
			return new WP_Error( 'upload_dir_error', $upload['error'] );

		// fetch the remote url and write it to the placeholder file
		$wp_http = new WP_Http();
		$response = $wp_http->request( $url, [ 'stream' => true, 'filename' => $upload['file'] ] );
		$headers = $response['headers'];

		// request failed
		if ( ! $response ) {
			@unlink( $upload['file'] );
			return new WP_Error( 'import_file_error', __('Remote server did not respond', 'wordpress-importer') );
		}

		// make sure the fetch was successful
		if ( $response['response']['code'] != '200' ) {
			@unlink( $upload['file'] );
			return new WP_Error( 'import_file_error', sprintf( __('Remote server returned error response %1$d %2$s', 'wordpress-importer'), esc_html($headers['response']), get_status_header_desc($headers['response']) ) );
		}

		$filesize = filesize( $upload['file'] );

		if ( isset( $headers['content-length'] ) && $filesize != $headers['content-length'] ) {
			@unlink( $upload['file'] );
			return new WP_Error( 'import_file_error', __('Remote file is incorrect size', 'wordpress-importer') );
		}

		if ( 0 == $filesize ) {
			@unlink( $upload['file'] );
			return new WP_Error( 'import_file_error', __('Zero size file downloaded', 'wordpress-importer') );
		}

		$max_size = (int) $this->max_attachment_size();
		if ( ! empty( $max_size ) && $filesize > $max_size ) {
			@unlink( $upload['file'] );
			return new WP_Error( 'import_file_error', sprintf(__('Remote file is too large, limit is %s', 'wordpress-importer'), size_format($max_size) ) );
		}

		// keep track of the old and new urls so we can substitute them later
		$this->url_remap[$url] = $upload['url'];
		$this->url_remap[$post['guid']] = $upload['url']; // r13735, really needed?
		// keep track of the destination if the remote url is redirected somewhere else
		if ( isset($headers['x-final-location']) && $headers['x-final-location'] != $url )
			$this->url_remap[$headers['x-final-location']] = $upload['url'];

		return $upload;
	}

Hopefully this or similar can be included in the core code if the developer has time