import error in 3.3.7

[Robert Ladyman]

Pip install of breezy 3.3.7 in a venv with Python 3.12.2 results in (when just using 'brz' from the bash prompt):

Error: PyErr { type: <class 'ImportError'>, value: ImportError('..._hashlib.cpython-312-x86_64-linux-gnu.so: undefined symbol: PyExc_ValueError')

Similar errors also occur with Python 3.11 and 3.10 (the last version I could get working with 3.3.7 of brz was Python 3.9.5).

To work with Python 3.12.1, breezy version 3.3.4 is needed.

I suspect this is a rust + venv error: while attempting to debug the issue, the failure seems to be something related to PyObject_Repr in brz's __main__.py when it imports breezy.commands. That is, main.rs fails at:

 let main = PyModule::import(py, "breezy.__main__")?;

and __main__.py at 'import breezy.commands'.

Debugging the rust code with:

        let sysconfig = PyModule::import(py, "sysconfig").unwrap();
        let python_version = sysconfig.call_method0("get_python_version").unwrap();
        eprintln!("Python version is {}", python_version);
        let python_lib = sysconfig.call_method("get_config_var", ("LIBDEST",), None).unwrap();
        eprintln!("Using python lib: {}", python_lib);
        let python_site_packages = sysconfig.call_method("get_path", ("purelib",), None).unwrap();
        eprintln!("Using python site-packages: {}", python_site_packages);
        let sys = PyModule::import(py, "sys").unwrap();
        let py_path:&str = sys.getattr("executable").unwrap().extract().unwrap();
        eprintln!("Path is {}", py_path);

seemed to show the correct paths / libraries but I suspect that there's an error with a mis-match of Python and its libraries and rust.

[Robert Ladyman (saccadic-masking)]

An additional note: it might be related to the change in https://bugs.launchpad.net/brz/+bug/1951258 (update_path())