Bug 2203820

The issue was originally reported as a GitHub issue on upstream: https://github.com/fedora-sysv/chkconfig/issues/102 and fixed by: https://github.com/fedora-sysv/chkconfig/pull/104

We have a problem in python3.11-wheel package which we can probably solve by ourselves but I think the strange behavior of alternatives I discovered is still worth reporting.

When talking about packages, I mean the ones available in RHEL 8 and I'm using 1minutetip for testing. The most important ones are chkconfig-1.19.1-1.el8.x86_64 and python3.11-wheel-0.38.4-3.el8.noarch.

To reproduce the problem on RHEL 8:

1. `dnf install python36 python3.11`  (Python 3.6 is needed later.)
2. `alternatives --set python3 /usr/bin/python3.11`
3. `dnf install python3.11-wheel`

The installation of python3.11-wheel calls [this command in its `%post` scriptlet](https://gitlab.com/redhat/centos-stream/rpms/python3.11-wheel/-/blob/c8s/python3.11-wheel.spec#L121-125):
`alternatives --keep-foreign --add-slave python3 /usr/bin/python3.11 /usr/bin/wheel-3 wheel-3 /usr/bin/wheel-3.11`

The command produces the following error:

```
Running scriptlet: python3.11-wheel-0.38.4-3.el8.noarch                                 1/1 
failed to link /usr/bin/wheel-3 -> /etc/alternatives/wheel-3: /usr/bin/wheel-3 exists and it is either not a symlink or --keep-foreign was set and link points outside /etc/alternatives
```

But, if you set the alternative for python3 to python36 which means that the installation of python3.11-wheel will add the slave into an inactive alternative, it works fine and no error is shown. So these steps are fine:

1. `dnf install python36 python3.11`
2. `alternatives --set python3 /usr/bin/python3.6`
3. `dnf install python3.11-wheel`

If I understand it correctly `--keep-foreign` should prevent the `--add-slave` from removing/changing a symlink, if it already exists. If that's true, having `--add-slave` together with `--keep-foreign` makes perfect sense. The problem is that the error message is not true: `/usr/bin/wheel-3` does not exist in this case. Alternatives should create that file if you install python3.11-wheel when python3.11 is the active alternative for python3.

To sum this up:
* If python3.11 is active alternative for python3, the installation of python3.11-wheel does not create `/usr/bin/wheel-3` and shows the error mentioned above.
* If python36 is active alternative for python3, the installation succeedes without errors. Then, when you switch from python36 to python3.11 alternative, the file `/usr/bin/wheel-3` is there and works as expected: `/usr/bin/wheel-3 -> /etc/alternatives/wheel-3 -> /usr/bin/wheel-3.11`.

Bug report with some more context: https://bugzilla.redhat.com/show_bug.cgi?id=2181479

Does it make sense to use `--keep-foreign` with `--add-slave`? If so, could we fix the problem? And if not, could we improve the error message to make it clear that this is not supported?