private function runProcesses(OutputInterface $output)
    {
        $progress = new ProgressIndicator($output);
        $progress->start('Starting...');

        // Start all of the processes.
        foreach ($this->processes as $process) {
            $process->start();
            $progress->advance();
        }

        // Wait for each to be done.
        foreach ($this->processes as $name => $process) {
            $progress->setMessage(sprintf('Waiting for moodle-plugin-ci %s...', $name));
            while ($process->isRunning()) {
                $progress->advance();
            }
        }
        $progress->finish('Done!');
    }