Commands python-add-import, python-remove-imports and
python-sort-imports run a short Python script stored in variable
python--list-imports; That script starts with:

    from isort import find_imports_in_stream, find_imports_in_paths

But find_imports_in_stream and find_imports_in_paths were introduced in
version 5.7.0 of the isort library.

Debian bookworm has isort version 5.6.4 in its package repositories.
Thus on such system commands python-add-import, python-remove-import
and python-sort-imports fail with error message:

    python exited with status 1 (maybe isort is missing?)

This is misleading when the isort library is installed.

I suggest to extend the Python script in order to catch the import
errors and return status 1 if the isort library is not found and status
2 if the expected symbols aren't found.  The error message can then be
specialized.  This is what I implemented in the attached patch.