Ticket #28013: 28013.diff

wp-admin/includes/class-wp-upgrader.php

@@ -431 +431 @@
                         $this->skin->feedback('maintenance_start');
                         // Create maintenance file to signal that we are upgrading
                         $maintenance_string = '<?php $upgrading = ' . time() . '; ?>';
-                        $wp_filesystem->delete($file);
+                        if( is_file( ABSPATH . '.maintenance' ) ) {
+                                $wp_filesystem->delete($file, false, 'f');
+                        }
                         $wp_filesystem->put_contents($file, $maintenance_string, FS_CHMOD_FILE);
-                } else if ( !$enable && $wp_filesystem->exists($file) ) {
+                } else if ( !$enable && is_file( ABSPATH . '.maintenance' ) ) {
                         $this->skin->feedback('maintenance_end');
-                        $wp_filesystem->delete($file);
+                        $wp_filesystem->delete($file, false, 'f');
                 }
         }