Now all modules are in core modules folder

modules/customerror/customerror.install

@@ -0,0 +1,19 @@
+<?php
+
+/**
+ * @file
+ * Install and uninstall hooks.
+ */
+
+/**
+ * Implements hook_uninstall().
+ */
+function customerror_uninstall() {
+  db_query("DELETE FROM {variable} WHERE name LIKE 'customerror_%'");
+
+  foreach (_customerror_enum_errors() as $code => $desc) {
+    if (variable_get('site_' . $code, '') == 'customerror/' . $code) {
+      variable_del('site_' . $code, '');
+    }
+  }
+}