Modify all the similar Python test wrappers to set
`G_DEBUG=fatal-warnings` in the environment of the program being tested,
so we can catch unexpected warnings/criticals.
Adding this because I noticed it was missing, not because I noticed a
warning/critical was being ignored.
Signed-off-by: Philip Withnall <philip@tecnocode.co.uk>
In case we're out of memory we should abort after having printed an error
message, this is similar to crashing but not exactly the same, so ensure
we exit for SIGABRT and not because of a SIGSEV.
We use a test wrapper to ensure that both the exit code and the stderr
match what we expected.
