When Tuleap want to remove the plugins caches it loads it first which could lead to warnings when data in the cache is invalid (e.g. removal of the RPM package of a plugin).

You get this kind of warnings (in this example RPM of the pullrequest package has been removed):

Warning: include_once(/usr/share/tuleap/plugins///pullrequest/include/pullrequestPlugin.class.php): failed to open stream: No such file or directory in /usr/share/tuleap/src/common/plugin/PluginManager.class.php on line 105
PHP Warning: include_once(): Failed opening '/usr/share/tuleap/plugins///pullrequest/include/pullrequestPlugin.class.php' for inclusion (include_path='/usr/share/php:/usr/share/pear:/usr/share/tuleap/src/www/include:/usr/share/tuleap/src:/usr/share/codendi/src/www/include:/usr/share/codendi/src:/usr/share/jpgraph:.:/usr/share/htmlpurifier:/usr/share/jpgraph') in /usr/share/tuleap/src/common/plugin/PluginManager.class.php on line 105