Diffusion - upgrade exception error message to include hint to config option

Summary: Fixes T6419. Also, there was a question on T6419 about whether this was in a try catch block and it is... Its not clear to me what happens in the "timeout" case though?

Test Plan: looks nice

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T6419

Differential Revision: https://secure.phabricator.com/D10755