This commit adds a tiny unit test for the new `shlex` based
os-release parsing and tweaks the error message in a small
and non-functional way (just because it's slightly nicer
for a user). The test checks for three keys NAME which is
quoted with `"`, ID which is not quoted and OSTREE_VERSION
which is quoted with `'`.
- Replaced string stripping with `shlex.split()` to properly
handle values in the os-release file;
- This ensures cleaner and more accurate key-value assignments,
follwing a broader set of shell-like parsing rules;
- Add os-release file for Fedora CoreOS 40 for testing.
Signed-off-by: Renata Ravanelli <rravanel@redhat.com>
