[Evolution] evolution 3.20.5 fails again with lockup on opening "Generating message list"

[john lauterbachandassociates net]

This is second time this failure has occurred in two weeks.  Following 
instructions I received from this list two weeks ago, I did the quick 
test, go to ~/.config/evolution and as a starter rename the 'mail'
subfolder to something else, like 'mail.old', and then start the 
evolution.  This did not work then and it did not work with this 
afternoon's failure.

What worked two weeks ago was to rename ~/.local/share/evolution/mail to 
~/.local/share/evolution/mail.old.  Evolution started up correctly, but 
I had lost all my existing e-mail.  I completed recovery of that lost 
e-mail, by copying each folder under mail.old to mail.

Everything was fine until this afternoon, when a new version of Ubuntu 
base was installed.  When I rebooted to complete that upgrade, evolution 
failed.

Version of evolution is 3.20.5.  There is no debug package for 3.20.5 .  
Please note that up until two weeks ago, 3.20.5 had worked perfectly, 
indeed best version of evolution to date.

In case anyone is interested, OS is Ubuntu 16.04 64-bit.

What are next steps?

John