Ticket #52915: 52915.diff

src/wp-includes/user.php

@@ -149 +149 @@
         if ( ! $user ) {
                 return new WP_Error(
                         'invalid_username',
-                        __( '<strong>Error</strong>: Unknown username. Check again or try your email address.' )
+                        sprintf(
+                                /* translators: %s: User name. */
+                                __( '<strong>Error</strong>: Unknown username. The username <strong>%s</strong> is not registered on this site. If you&#8217;re unsure of your username, you can attempt to login using your email address instead.' ),
+                                $username
+                        )
                 );
         }