Fix for deadlock in python callback

[sgonorov]

Fix update from release branch

[Copilot]

Pull request overview

This PR fixes a deadlock issue in Python callbacks by ensuring proper GIL (Global Interpreter Lock) management during callback lifecycle. The fix addresses the problem of Python objects being destroyed without holding the GIL, which can cause deadlocks in multi-threaded scenarios.

Key changes:

• Updated callback signature to use py::str instead of std::string for better Python integration
• Added custom deleters to shared pointers that acquire GIL before destroying Python objects
• Improved error handling in UTF-8 string decoding with null pointer checks

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
src/python/py_utils.hpp	Changed callback signature from std::string to py::str parameter
src/python/py_utils.cpp	Added GIL-aware custom deleters for Python callbacks and improved UTF-8 decoding error handling

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[Wovchena]

What are the results of running tests without acquired GIL? Do the really fail and this code is required?

[sgonorov]

Yes, if GIL is not there it means we have undefined behaviour, it fails from time to time.

[Wovchena]

Why not gil_scoped_acquire?

[sgonorov]

Replaced it with gil_scoped_acquire - I've tried using C-api to check how it works. But looks like it doesn't make any difference.