Index: src/wp-includes/class-http.php
===================================================================
--- src/wp-includes/class-http.php	(revision 50388)
+++ src/wp-includes/class-http.php	(working copy)
@@ -400,7 +400,10 @@
 			// Add the original object to the array.
 			$response['http_response'] = $http_response;
 		} catch ( Requests_Exception $e ) {
-			$response = new WP_Error( 'http_request_failed', $e->getMessage() );
+			$order = array_diff( mb_detect_order(), [ 'UTF-8' ] );
+			$order[] = 'UTF-8';
+			$response = new WP_Error( 'http_request_failed',
+				mb_convert_encoding( $e->getMessage(), 'UTF-8', mb_detect_encoding( $e->getMessage(), $order, true ) ) );
 		}
 
 		reset_mbstring_encoding();