The root cause was a 2nd `context.Context()` that was used in
`constructTestJob()`, which cancelled when that function returned.
The cancellation of the context caused an interrupt in the SQLite
driver, which got into a race condition and could cause an interrupt on
a subsequent database query.
The on-disk database that was used before caused issues with tests running
in parallel. Not only is there the theoretical issue of tests seeing each
other's data (this didn't happen, but could), there was also the practical
issue of one test running while the other tried to erase the database file
(which fails on Windows due to file locking).
