General: Further improve error messages following [42648].

Props kristastevens, melchoyce.
Fixes #38332 for trunk.


Built from https://develop.svn.wordpress.org/trunk@42719


git-svn-id: http://core.svn.wordpress.org/trunk@42547 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/file.php

@@ -591,7 +591,7 @@ function wp_edit_theme_plugin_file( $args ) {
 			}
 
 			if ( ! isset( $result['message'] ) ) {
-				$message = __( 'An error has occurred.' );
+				$message = __( 'Something went wrong.' );
 			} else {
 				$message = $result['message'];
 				unset( $result['message'] );