[נפתר] WPML 4.7.3 has failed to update properly and I am unable to login to WordPress now

Background of the issue:
I was trying to update WPML to the latest 4.7.3 patch.

Symptoms:
WPML 4.7.3 has failed to update properly, and I am unable to login to WordPress. There has been a critical error on this website. Please check your site admin email inbox for instructions. If you continue to have problems, please try the support forums.

Questions:
Why did the WPML 4.7.3 update fail?
How can I resolve the critical error preventing me from logging into WordPress?