Every so often, someone encounters a bad database upgrade. This often

comes from in-house modifications, canceled upgrades, or an upgrade from

some particular versions where Django Evolution or Django had some bad

behavior in their SQL or project signature generation.
To help diagnose these issues, this change logs useful information when

either the project signature diff is non-empty (indicating missing

evolution state) or an upgrade fails due to an error. The contents of

the log include:

Any useful error messages
A project signature diff
Lists of applied evolutions and migrations
Lists of pending evolutions
The current stored signature
Timestamps of all stored signatures
An information (but not schema) dump of the database

Ideally we'd also log the SQL schema, but that'd require some

per-database logic for correctly running each one's SQL dumping command.

Instead, we'll leave that to something handled during support.
There are also fixes for typos in the output message, and more detail

in the upgrade failure message.
This is something I've had on the backburner for a long time, but a

recent hard-to-diagnose failure in CI helped incentivize building this

logic. Hopefully it will help in the future when customers reach out

with problems.

Simulated different failures, both at signature diff time and upgrade

time. Checked the resulting log file and the output for errors.