The `%__os_install_post` macro is run after the %install section of each RPM build. It launches the `brp-python-bytecompile` script that is supposed to bytecompile all Python scripts that haven't been bytecompiled already.

The Python 3.11 stack was added to both RHEL 8 and 9. On RHEL 9 the brp-python-bytecompile script is newer and is prepared for Python 3.11, but on RHEL 8 it isn't. Thus Python 3.11 scripts that weren't bytecompiled as part of the %build or %install sections are left uncompiled.

Tested in Copr: https://copr.devel.redhat.com/coprs/torsava/python3.11-test-os-install-post-bytecompile/

Spec file changes to reproduce:

```
...
%install
mkdir -p %

{buildroot}%{python3_sitelib}/directory/
echo "print()" > %{buildroot}

%

{python3_sitelib}/directory/hugo.py
...

%check
echo "============== Print .py files found =================="
find %{buildroot}%{python3_sitelib}

/directory/ -name "*.py"
echo "============== Print .pyc files found =================="
find %

{buildroot}%{python3_sitelib}/directory/ -name "*.py[co]"
echo "============== End of print =================="

# Count .py and .pyc files
PY=$(find %{buildroot}

%

{python3_sitelib}/directory/ -name "*.py" | wc -l)
PYC=$(find %{buildroot}%{python3_sitelib}

/directory/ -name "*.py[co]" | wc -l)
test $PY -eq 1
test $(expr $PY * 2) -eq $PYC
...
```

Output for .py files is the same on RHEL 8 & 9:

============== Print .py files found ==================
+ find /builddir/build/BUILDROOT/python3.11-wheel-0.38.4-3.el9.x86_64/usr/lib/python3.11/site-packages/directory/ -name '*.py'
/builddir/build/BUILDROOT/python3.11-wheel-0.38.4-3.el9.x86_64/usr/lib/python3.11/site-packages/directory/hugo.py

But for .pyc it's different:

RHEL 9:

+ echo '============== Print .pyc files found =================='
+ find /builddir/build/BUILDROOT/python3.11-wheel-0.38.4-3.el9.x86_64/usr/lib/python3.11/site-packages/directory/ -name '*.py[co]'
/builddir/build/BUILDROOT/python3.11-wheel-0.38.4-3.el9.x86_64/usr/lib/python3.11/site-packages/directory/_pycache_/hugo.cpython-311.opt-1.pyc
/builddir/build/BUILDROOT/python3.11-wheel-0.38.4-3.el9.x86_64/usr/lib/python3.11/site-packages/directory/_pycache_/hugo.cpython-311.pyc
============== End of print ==================

RHEL 8:

+ echo '============== Print .pyc files found =================='
+ find /builddir/build/BUILDROOT/python3.11-wheel-0.38.4-3.el8.x86_64/usr/lib/python3.11/site-packages/directory/ -name '*.py[co]'
============== End of print ==================