GDate test suite fails when parsing Polish
ERROR:../../../glib-2.58.0/glib/tests/date.c:384:test_month_names: assertion failed (g_date_get_month (gdate) == 9): (8 == 9)
That's this line in the pl_PL test:
TEST_DATE ( 1, 9, 2018, "%OB %Y", "wrzesień 2018");
I'm starting to think the CI machines need more locales installed.