Ticket #27196: remove-first.diff

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

@@ -52 +52 @@
                 $this->strings['installing_package'] = __('Installing the latest version…');
                 $this->strings['no_files'] = __('The package contains no files.');
                 $this->strings['folder_exists'] = __('Destination folder already exists.');
+                $this->strings['remove_first'] = __('You cannot install over the top of an already existing entity - you need to de-install the existing version first.');
                 $this->strings['mkdir_failed'] = __('Could not create directory.');
                 $this->strings['incompatible_archive'] = __('The package could not be installed.');
 
@@ -364 +365 @@
                 $this->skin->set_result($result);
                 if ( is_wp_error($result) ) {
                         $this->skin->error($result);
+                        if (@in_array('folder_exists', $result->get_error_codes())) $this->skin->feedback('remove_first');
                         $this->skin->feedback('process_failed');
                 } else {
                         //Install Succeeded