The `shutil.rmtree(onerror=...)` kwarg got deprecated with py3.12.
We still need to support older version of python all the way
back to 3.6 so just ignore this pylint error for a while.
The current implementation of `rmtree` will try to fix permissions
when it encounters permission errors during its operation. This is
done by opening the target via `os.open` and then adjusting the
immutable flag and the permission bits. This is a problem when the
target is a broken symlink since open will fail with `ENOENT`. A
simple reproducer of this scenario is:
$ mkdir subdir
$ ln -s foo subdir/broken
$ chmod a-w subdir/
$ python3 -c 'import osbuild; osbuild.util.rmrf.rmtree("subdir")'
Since subdir is not writable, removing `subdir/broken` will fail
with `EPERM` and the `on_error` callback will try to fix it by
invoking `fixperms` on `subdir/broken` which will in `open` since
the target does not exist (broken symlink).
This is fixed by using `O_NOFOLLOW` to open so we will never open
the target. Instead `open` will fail with `ELOOP`; we ignore that
error and in fact we ignore now all errors from `open` since it
does not matter: if fixing the permissions didn't work `unlink`
will just fail (again) with `EPERM` and for symlinks it actually
doesn't matter since "on Linux the permissions of an ordinary
symbolic link are not used in an operations", see symlinks(7).
Make use of the new immutable-flag ioctl helpers. While at it, move the
`chmod` to `fchmod` and re-use the open file-descriptor. Document the
behavior and move the `fchmod` into its own try-block for the same
reasons as the `ioctl` call: We rely on the following unlink() to catch
any errors. Errors in the fixperms() step are non-consequential.
Move remove_tree() into its own module in `osbuild.util.rmrf`. This way
we can use it in other modules as well, without cross-referencing
internal helpers.
