PythonAPI: Fix segfaults due to incorrect GIL locking

[wentasah]

When using CARLA with Python 3.10, I'm getting a segfault in GetAvailableMaps. The problem disappears when PyList manipulation does not happen with GIL unlocked, as done in this commit.

The initial part of crash backtrace (from GDB) is below:

Program terminated with signal SIGSEGV, Segmentation fault.

warning: Section `.reg-xstate/49253' in core file too small.
#0  _PyInterpreterState_GET () at ./Include/internal/pycore_pystate.h:117
117	   return tstate->interp;
[Current thread is 1 (Thread 0x7fe6fe48f740 (LWP 49253))]
(gdb) bt
#0  _PyInterpreterState_GET () at ./Include/internal/pycore_pystate.h:117
#1  get_list_state () at Objects/listobject.c:26
#2  PyList_New (size=0) at Objects/listobject.c:159
#3  0x00007fe6fdc0dab0 in boost::python::detail::list_base::list_base() () from /nix/store/c95f3nrkz3sflvycihyw1c8q4nk47p4m-boost-1.79.0/lib/libboost_python310.so.1.79.0
#4  0x00007fe6ef9ecfc4 in boost::python::list::list (this=0x7ffd8a8aae28) at include/boost/python/list.hpp:61
#5  GetAvailableMaps (self=...) at source/libcarla/Client.cpp:26
#6  0x00007fe6efb6a8fe in boost::python::detail::invoke<boost::python::to_python_value<boost::python::list const&>, boost::python::list (*)(carla::client::Client const&), boost::python::arg_from_python<carla::client::Client const&> > (rc=..., f=<optimized out>, ac0=...)
    at include/boost/python/detail/invoke.hpp:73
#7  boost::python::detail::caller_arity<1u>::impl<boost::python::list (*)(carla::client::Client const&), boost::python::default_call_policies, boost::mpl::vector2<boost::python::list, carla::client::Client const&> >::operator() (args_=<optimized out>, this=<optimized out>)
    at include/boost/python/detail/caller.hpp:233
#8  boost::python::objects::caller_py_function_impl<boost::python::detail::caller<boost::python::list (*)(carla::client::Client const&), boost::python::default_call_policies, boost::mpl::vector2<boost::python::list, carla::client::Client const&> > >::operator() (
    this=<optimized out>, args=<optimized out>, kw=<optimized out>) at include/boost/python/object/py_function.hpp:38
#9  0x00007fe6fdc1b4dd in boost::python::objects::function::call(_object*, _object*) const () from /nix/store/c95f3nrkz3sflvycihyw1c8q4nk47p4m-boost-1.79.0/lib/libboost_python310.so.1.79.0
#10 0x00007fe6fdc1b6a8 in boost::detail::function::void_function_ref_invoker0<boost::python::objects::(anonymous namespace)::bind_return, void>::invoke(boost::detail::function::function_buffer&) ()
   from /nix/store/c95f3nrkz3sflvycihyw1c8q4nk47p4m-boost-1.79.0/lib/libboost_python310.so.1.79.0
...

Description

Fixes #

Where has this been tested?

• Platform(s): Linux
• Python version(s): 3.10
• Unreal Engine version(s): default in 0.9.14

Possible Drawbacks

---

This change is 

[update-docs]

Thanks for opening this pull request! The maintainers of this repository would appreciate it if you would update our CHANGELOG.md based on your changes.

[wentasah]

Added a changelog entry and rebased to dev.

[javiergrCS]

The code changes proposed by the collaborator wentasah have been successfully tested, verifying that they fix the segfault affecting the GetAvailableMaps function when using Python 3.10. The changes are ready to be merged and integrated into the 'dev' branch.

[wentasah]

Thanks for the review @javiergrCS.

In the mean time, I've found a similar segfault in get_random_location_from_navigation(). I added a commit fixing this segfault too.

[javiergrCS]

The changes proposed by the collaborator wentasah for the function get_random_location_from_navigation() have been successfully tested, and it has been verified that these changes fix the issue with that function. The changes are ready to be merged into the 'dev' branch.

Thank you for your collaboration, wentasah.

[bernatx]

Reviewed 1 of 1 files at r2, 1 of 2 files at r3, 1 of 1 files at r4, all commit messages.
Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @Harin22)

[bernatx]

Reviewable status: all files reviewed, 1 unresolved discussion (waiting on @Harin22)