Log directory for permission denied errors
Was getting:
mkdir(): Permission denied
/var/www/cms/docroot/vendor/weitzman/drupal-test-traits/src/GoutteTrait.php:56
/var/www/cms/docroot/vendor/weitzman/drupal-test-traits/src/ExistingSiteBase.php:53
Found that it was:
$output_dir = getenv('BROWSERTEST_OUTPUT_DIRECTORY');
and in phpunit.xml I had <env name="BROWSERTEST_OUTPUT_DIRECTORY" value="/app/docroot/sites/simpletest/browser_output"/>
which was my problem.
Would be nice to have the directory that errored out displayed in output.
Cross-linking D.O issue here https://www.drupal.org/project/drupal/issues/2867042