code: public function dispatchInstallerEvent($eventName, $devMode, PolicyInterface $policy, Pool $pool, CompositeRepository $installedRepo, Request $request, array $operations = array())
      {
          return $this->doDispatch(new InstallerEvent($eventName, $this->composer, $this->io, $devMode, $policy, $pool, $installedRepo, $request, $operations));
      }
docs: Dispatch a installer event.
  
  @param string              $eventName     The constant in InstallerEvents
  @param bool                $devMode       Whether or not we are in dev mode
  @param PolicyInterface     $policy        The policy
  @param Pool                $pool          The pool
  @param CompositeRepository $installedRepo The installed repository
  @param Request             $request       The request
  @param array               $operations    The list of operations
  
  @return int return code of the executed script if any, for php scripts a false return
  value is changed to 1, anything else to 0