We recently moved to Drupal 9.3.0 with a composer file layout and Drush 11.0. We make use of Drush Scripts to execute website functions from Crontab. One specific case is sending a newsletter email early each morning.
I receiving the subject error from a Drush Script that has been running for years. The script is executed by moving into the webroot directory of the website and running
drush scr email_script.php arg1 arg2. The first thing the Drush Script does is pull the arguments from the command line using
drush_shift() but this function is not defined. I'm not sure how to proceed in debugging this.