[PATCH v2] Fix Python3.9 related runtime problems

[Tom Tromey]

>>>>> "Kevin" == Kevin Buettner via Gdb-patches <gdb-patches@sourceware.org> writes:

Kevin> [ This version removes the PY_VERSION_HEX preprocessor test from
Kevin>   do_start_initialization; PyEval_SaveThread() will now be used in
Kevin>   place of PyThreadState_Swap and PyEval_ReleaseLock for all Python
Kevin>   versions.  I rebuilt and retested on all OSes mentioned in the
Kevin>   commit log remarks below.  No problems encountered.  ]

Looks good to me.  Thanks for doing this.

Tom