tests: Adapt to glib 2.87.0

[ppisar]

After upgrading glib from 2.86.1 to 2.87.0, tests which expect catching SIGTRAP started to fail like this:

[...]/redhat-linux-build/modulemd/component_module
TAP version 14
# random seed: R02S501b6bd02413a2980133f197dab99416
1..6
# Start of modulemd tests
# Start of v2 tests
# Start of component tests
# Start of module tests
not ok /modulemd/v2/component/module/construct - libmodulemd-FATAL-CRITICAL: modulemd_component_set_key: assertion 'name' failed
Bail out!
Aborted                    (core dumped) LD_LIBRARY_PATH=/home/test/libmodulemd-devel/redhat-linux-build/modulemd MESON_BUILD_ROOT=/home/test/libmodulemd-devel/redhat-linux-build TEST_DATA_PATH=/home/test/libmodulemd-devel/modulemd/tests/test_data UBSAN_OPTIONS=halt_on_error=1:abort_on_error=1:print_summary=1:print_stacktrace=1 MSAN_OPTIONS=halt_on_error=1:abort_on_error=1:print_summary=1:print_stacktrace=1 LC_ALL=C MESON_TEST_ITERATION=1 MESON_SOURCE_ROOT=/home/test/libmodulemd-devel MALLOC_PERTURB_=115 ASAN_OPTIONS=halt_on_error=1:abort_on_error=1:print_summary=1 /home/test/libmodulemd-devel/redhat-linux-build/modulemd/component_module

The tests passed a NULL pointer to libmodulemd object constructors and checked that glib raised a SIGTRAP signal. The new glib fixed https://gitlab.gnome.org/GNOME/glib/-/issues/3790 and as a side effect changed how the process is terminated: If the process runs under a debugger, a breakpoint trap is invoked or SIGTRAP raised, depending on the architecture. If the process does not run under a debugger, abort() is called, which raises SIGABRT and then after returning to glib SIGABRT disposition is reset and SIGABRT raised again to finally terminate the process. That means that catching signals is pointless because the process will be terminated nevertheless.

This patch adapts the tests by using a glib-sanctioned way of checking whether a process terminated abnormally instead of depending on a way a particular glib version implements.

This patch moves the trapping subtests into standalone tests because g_test_trap_subprocess() cannot handle multiple subtests in a single test function. It also removes pointless checks for a return value of a function which has just exited the process.

The same goes for Python tests (with
G_DEBUG=fatal-warnings,fatal-criticals) which originally went as far as checking whether and which signal was raised. This patch makes the Python tests passing regardless of G_DEBUG setting.

Implementation note: Python does not support annoymous block and context managers are not compatible with fork, hence this patch moves the blocks into named callables to be exectuted in a subprocess.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=2423153

[ppisar]

The new way of running tests in a subprocess does work on old glib. I will implement a fallback.

[ppisar]

Now it builds everywhere. Mandriva has again (still?) broken dependencies in its packages.