Comment 63 for bug 1662531

totally by accident, I happened to have some debugging code in the routine desktop-widget.cpp. The debugging code looks like this:
    std::cout << "sp_dtw_rotation_output before locale()" << std::endl;
 s.imbue(std::locale(""));;

it was intended to track occurrences of the offending call. When I run your debugging code with localize off, I get the following Python window with data:

sp_dtw_rotation_output before locale()

sp_dtw_rotation_output before locale()

sp_dtw_rotation_output before locale()

sp_dtw_rotation_output before locale()

so, four calls to the offending code, but no crash.

when I run your code with localize on, I get the following output:
sp_dtw_rotation_output before locale()

sp_dtw_rotation_output before locale()

so, two calls, plus a crash.