Here's a chunk of the call stack from the Visual Studio debugger using the debug build. Py_FatalError seems to be called multiple times:

>   ucrtbased.dll!72d27f30()    Unknown
    [Frames below may be incorrect and/or missing, no symbols loaded for ucrtbased.dll] 
    [External Code] 
    python35_d.dll!Py_FatalError(const char * msg) Line 1375    C   
    python35_d.dll!_Py_CheckRecursiveCall(const char * where) Line 733  C
    python35_d.dll!PyObject_Call(_object * func, _object * arg, _object * kw) Line 2144 C
    python35_d.dll!call_function_tail(_object * callable, _object * args) Line 2173 C
    python35_d.dll!callmethod(_object * func, const char * format, char * va, int is_size_t) Line 2242  C 
    python35_d.dll!_PyObject_CallMethodId(_object * o, _Py_Identifier * name, const char * format, ...) Line 2287   C
    python35_d.dll!flush_std_files() Line 488   C   
    python35_d.dll!Py_FatalError(const char * msg) Line 1354    C   
    python35_d.dll!_Py_CheckRecursiveCall(const char * where) Line 733  C
    python35_d.dll!PyObject_Call(_object * func, _object * arg, _object * kw) Line 2144 C
    python35_d.dll!do_call(_object * func, _object * * * pp_stack, int na, int nk) Line 4883    C       python35_d.dll!call_function(_object * * * pp_stack, int oparg) Line 4679   C
    python35_d.dll!PyEval_EvalFrameEx(_frame * f, int throwflag) Line 3183  C
    python35_d.dll!fast_function(_object * func, _object * * * pp_stack, int n, int na, int nk) Line 4751   C
    python35_d.dll!call_function(_object * * * pp_stack, int oparg) Line 4677   C
    python35_d.dll!PyEval_EvalFrameEx(_frame * f, int throwflag) Line 3183  C
    python35_d.dll!fast_function(_object * func, _object * * * pp_stack, int n, int na, int nk) Line 4751   C
    python35_d.dll!call_function(_object * * * pp_stack, int oparg) Line 4677   C
    python35_d.dll!PyEval_EvalFrameEx(_frame * f, int throwflag) Line 3183  C
    python35_d.dll!_PyEval_EvalCodeWithName(_object * _co, _object * globals, _object * locals, _object * * args, int argcount, _object * * kws, int kwcount, _object * * defs, int defcount, _object * kwdefs, _object * closure, _object * name, _object * qualname) Line 3962    C 
    python35_d.dll!fast_function(_object * func, _object * * * pp_stack, int n, int na, int nk) Line 4760   C