The helper "progress" is not defined when translate:cleanup

[ritterg]

When I try to clean up translations I get the error

[Symfony\Component\Console\Exception\InvalidArgumentException]
The helper "progress" is not defined.

There seems to be a problem with ProgressHelper (removed from Symfony)

The Progress Helper was deprecated in Symfony 2.5 and removed in Symfony 3.0. You should now use the Progress Bar instead which is more powerful.

A quick fix for me (in CleanUpCommand.php) was to include ProgressBar
use Symfony\Component\Console\Helper\ProgressBar;

replace line 64
$this->progress = $this->getHelperSet()->get('progress');
by
$this->progress = new ProgressBar($this->output, 50);
(Note: 50 is an arbitrary number, should be replaced by the real number of files)

and replace line 102
$this->progress->start($this->output, count($lines, COUNT_RECURSIVE));
by
$this->progress->start();

Only a quick fix, but maybe a starting point?