Error while updating
just to make you aware in case you're using the Pathauto module and you didn't notice:


  Changes to path aliases and a critical note for sites using the Pathauto contributed module
  If you have the contributed Pathauto module enabled, you must update to the latest version of Pathauto before you update to Drupal 8.8.0. Failure to update Pathauto before updating core could result in data loss. Drupal 8.8.0 declares a conflict with Pathauto 8.x-1.5 or lower for this reason.


https://www.drupal.org/project/drupal/releases/8.8.0

Can't say anything about your specific error though.