Progressbar is by default redirected to stderr.
That's fine, if I could simple change output to stdout.

Example

Given errors from cron are logged to file:

* * * * *       app/console something 1> /dev/null 2>> app/logs/cron.log

After upgrade to symfony 2.8 the file contains:

$ cat app/logs/cron.log

 0/3 [>---------------------------]   0%
 1/3 [=========>------------------]  33%
 2/3 [==================>---------]  66%
 3/3 [============================] 100%

Why?

#15795 sets getErrorOutput in constructor. Provided solution:

If someone explicitly wants to use stdout, they can simply pass $output->getStream() instead of $output in most use-cases.

doesn't work because:

  [Symfony\Component\Debug\Exception\ContextErrorException]
  Catchable Fatal Error: Argument 1 passed to Symfony\Component\Console\Helper\ProgressBar::__construct() must implement interface Symfony\Component\Console\Output\OutputInterface, resource given, called in /Users/www/ter_004_gosms/src/Analytics/Command/SmsReportingC
  ommand.php on line 41 and defined

Solution

Temporarily I solved it with creating another output:

    protected function execute(InputInterface $input, OutputInterface $output)
    {
        $stdout = new \Symfony\Component\Console\Output\StreamOutput($output->getStream());
        $progressBar = new ProgressBar($stdout);
    }

That's not very good developer experience. I had to search github issues, PR, symfony/console code...
Printing progress to stdout should be at least mentioned in documentation