We run tests using tox to set up environments for different python
versions to test against. The problem is that when a test shells out to
a python script, like osbuild-depsolve-dnf5, it's not run inside the
environment but in the system environment. The `has_dnf5()` check
returns False because it fails to import dnf5 in the tox environment,
even though the script can be run and the test will succeed.
Use `python3 -c "import libdnf5"` to decide if the script is runnable
instead of using `importlib`. This doesn't solve the problem of our
tests running python scripts in a different environment than the one (we
think) we are testing, but it will enable tests of osbuild-depsolve-dnf5
for now.
562d30cf59