I have set up some custom symfony project-level settings in the file config/project.yml following the suggestion in How to manage your own cross-apps/global configuration values. Following these instructions I added the line
require_once sfConfigCache::getInstance()->checkConfig('config/project.yml');
to the configure method of my client application's clientConfiguration.class.php file. 
I then created a new symfony task using php symfony generate:task. In this new task I want to access the settings in the config/project.yml file. Here is the execute portion of the task: 
protected function execute($arguments = array(), $options = array()){
  // initialize the database connection
  $databaseManager = new sfDatabaseManager($this->configuration);
  $connection = $databaseManager->getDatabase($options['connection'])->getConnection();
  $configuration = ProjectConfiguration::getApplicationConfiguration('client', 'test', true);
  echo sfConfig::get('project_mail_webmaster') . "\n" ;
}
However, when I run the task I get this error:
PHP Fatal error:  Call to undefined method sfConfigCache::getInstance() in /opt/sfproject/apps/client/config/clientConfiguration.class.php on line 7
http://trac.symfony-project.org/wiki/HowToHandleCrossAppsConfigurationFiles
 
    