As of 2019-12-21, don't upgrade your Drupal from 8.7.x to 8.8.x. I did that mistake yesterday. I upgraded this website from Drupal 8.7.10 to 8.8.1. After the upgrade, I got the famous blank page with the message The website has encountered an error.. Then, I played around with different versions, and I got a better error message:
One or more problems were detected with your Drupal installation. Check the status report for more information. Modules could not be listed due to an error: The 'core' or the 'core_version_requirement' key must be present in core/modules/path_alias/path_alias.info.yml
With this error message, I was able to find that in 8.8.0, path core module is split into 2 modules: path and path_alias. This is the cause of my problem. In the release notes, they say to upgrade to the latest version of Pathauto before upgrading to 8.8.0. That is what did before knowing this. My Pathauto version was 8.x-1.6.
Anyway, after spending more than 3 hours trying to solve this issue in vain, I gave up. I restored the website using yesterday's backup.
I should have followed my own rule: Don't upgrade to the latest release right away, wait for at least 2 weeks.
I'm currently monitoring the following issues queue: