Wrap the SQLite error "interrupted (9)". That error is (as far as I
could figure out) caused by the context being closed. Unfortunately
there is no wrapping of the underlying context error, so it's not
possible to determine whether it was due to a 'deadline exceeded' error
or another cancellation cause (like upstream HTTP connection closing).
Primarily this makes a rather unreliable unit test properly reliable.
The code under test could return either `context.DeadlineExceeded` or
the "interrupted (9)" error (GORM + SQLite doesn't reliably chose one or
the other), and now this is cleanly tested for.
7fd8eca8d9