tests/__init__.py keeps a run offline, its scratch under tmp/ and its
installer cache its own, but only discover -s tests -t . imported it.
discover tests ran with RETROBIOS_OFFLINE unset, scratch on the /tmp
tmpfs and the user's real installer cache, the setting in which e2e
fixtures had written into the shared .cache/large. Every test module now
imports the package first, and a test fails on a module that does not.
test_verify_listing.py took its line with the previous commit.
Lakka builds LIBRETRO_CORES minus the exclusions each project, device
and GLES image adds. Without a list, --target refused Lakka and its RPi1
pack carried firmware for cores the image does not build.
Abdessamad Derraz