private function checkPiwikIsNotInstalled()
{
if (!SettingsPiwik::isPiwikInstalled()) {
return;
}
\Piwik\Plugins\Login\Controller::clearSession();
$message = Piwik::translate('Installation_InvalidStateError', array('<br /><strong>', '</strong><a id="piwik-is-already-installed" href=\'' . Common::sanitizeInputValue(Url::getCurrentUrlWithoutFileName()) . '\'>', '</a>'));
Piwik::exitWithErrorMessage($message);
}