It's likely a regression caused by bpo-36842.

https://buildbot.python.org/all/#/builders/47/builds/2854

Example of failure:

======================================================================
FAIL: test_NULL_ob_type (test.test_gdb.PrettyPrintTests)
Ensure that a PyObject* with NULL ob_type is handled gracefully
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/var/lib/buildbot/slaves/enable-optimizations-bot/3.x.gps-debian-profile-opt.nondebug/build/Lib/test/test_gdb.py", line 533, in test_NULL_ob_type
    self.assertSane('id(42)',
  File "/var/lib/buildbot/slaves/enable-optimizations-bot/3.x.gps-debian-profile-opt.nondebug/build/Lib/test/test_gdb.py", line 504, in assertSane
    self.get_gdb_repr(source,
  File "/var/lib/buildbot/slaves/enable-optimizations-bot/3.x.gps-debian-profile-opt.nondebug/build/Lib/test/test_gdb.py", line 278, in get_gdb_repr
    self.fail('Unexpected gdb output: %r\n%s' % (gdb_output, gdb_output))
AssertionError: Unexpected gdb output: 'Breakpoint 1 at 0x201df0: file Python/bltinmodule.c, line 1217.\n[Thread debugging using libthread_db enabled]\nUsing host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".\n\nBreakpoint 1, builtin_id () at Python/bltinmodule.c:1217\n1217\t{\n#0  builtin_id () at Python/bltinmodule.c:1217\n#1  _PyMethodDef_RawFastCallKeywords () at Objects/call.c:650\n#2  _PyCFunction_FastCallKeywords (func=<built-in method id of module object at remote 0x7ffff6ea7180>, args=<optimized out>, nargs=<optimized out>, kwnames=<optimized out>) at Objects/call.c:736\n#3  call_function (kwnames=0x0, oparg=1, pp_stack=<synthetic pointer>, tstate=<optimized out>) at Python/ceval.c:4831\n#4  _PyEval_EvalFrameDefault () at Python/ceval.c:3347\n#5  PyEval_EvalFrameEx (throwflag=0, f=Frame 0x7ffff6e94800, for file <string>, line 1, in <module> ()) at Python/ceval.c:685\n#6  _PyEval_EvalCodeWithName () at Python/ceval.c:4173\n#7  PyEval_EvalCodeEx (closure=0x0, kwdefs=0x0, defcount=0, defs=, kwcount=0, kws=, argcount=0, args=, locals={\'__name__\': \'__main__\', \'__doc__\': None, \'__package__\': None, \'__loader__\': <type at remote 0x555555b0eed0>, \'__spec__\': None, \'__annotations__\': {}, \'__builtins__\': <module at remote 0x7ffff6ea7180>}, globals={\'__name__\': \'__main__\', \'__doc__\': None, \'__package__\': None, \'__loader__\': <type at remote 0x555555b0eed0>, \'__spec__\': None, \'__annotations__\': {}, \'__builtins__\': <module at remote 0x7ffff6ea7180>}, _co=<code at remote 0x7ffff6e3e5d0>) at Python/ceval.c:4202\n#8  PyEval_EvalCode (co=<code at remote 0x7ffff6e3e5d0>, globals={\'__name__\': \'__main__\', \'__doc__\': None, \'__package__\': None, \'__loader__\': <type at remote 0x555555b0eed0>, \'__spec__\': None, \'__annotations__\': {}, \'__builtins__\': <module at remote 0x7ffff6ea7180>}, locals={\'__name__\': \'__main__\', \'__doc__\': None, \'__package__\': None, \'__loader__\': <type at remote 0x555555b0eed0>, \'__spec__\': None, \'__annotations__\': {}, \'__builtins__\': <module at remote 0x7ffff6ea7180>}) at Python/ceval.c:662\n#9  run_eval_code_obj () at Python/pythonrun.c:1078\n#10 run_mod () at Python/pythonrun.c:1100\n#11 PyRun_StringFlags () at Python/pythonrun.c:987\n#12 PyRun_SimpleStringFlags () at Python/pythonrun.c:461\n#13 pymain_run_command (cf=, command=<optimized out>) at Modules/main.c:241\n#14 pymain_run_python (exitcode=) at Modules/main.c:522\n#15 _Py_RunMain () at Modules/main.c:610\n#16 pymain_main () at Modules/main.c:640\n#17 _Py_UnixMain (argc=<optimized out>, argv=<optimized out>) at Modules/main.c:664\n#18 __libc_start_main (main=<main>, argc=7, argv=, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=) at ../csu/libc-start.c:291\n#19 _start ()\n'
Breakpoint 1 at 0x201df0: file Python/bltinmodule.c, line 1217.
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".

Breakpoint 1, builtin_id () at Python/bltinmodule.c:1217
1217	{
#0  builtin_id () at Python/bltinmodule.c:1217
#1  _PyMethodDef_RawFastCallKeywords () at Objects/call.c:650
#2  _PyCFunction_FastCallKeywords (func=<built-in method id of module object at remote 0x7ffff6ea7180>, args=<optimized out>, nargs=<optimized out>, kwnames=<optimized out>) at Objects/call.c:736
#3  call_function (kwnames=0x0, oparg=1, pp_stack=<synthetic pointer>, tstate=<optimized out>) at Python/ceval.c:4831
#4  _PyEval_EvalFrameDefault () at Python/ceval.c:3347
#5  PyEval_EvalFrameEx (throwflag=0, f=Frame 0x7ffff6e94800, for file <string>, line 1, in <module> ()) at Python/ceval.c:685
#6  _PyEval_EvalCodeWithName () at Python/ceval.c:4173
#7  PyEval_EvalCodeEx (closure=0x0, kwdefs=0x0, defcount=0, defs=, kwcount=0, kws=, argcount=0, args=, locals={'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': <type at remote 0x555555b0eed0>, '__spec__': None, '__annotations__': {}, '__builtins__': <module at remote 0x7ffff6ea7180>}, globals={'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': <type at remote 0x555555b0eed0>, '__spec__': None, '__annotations__': {}, '__builtins__': <module at remote 0x7ffff6ea7180>}, _co=<code at remote 0x7ffff6e3e5d0>) at Python/ceval.c:4202
#8  PyEval_EvalCode (co=<code at remote 0x7ffff6e3e5d0>, globals={'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': <type at remote 0x555555b0eed0>, '__spec__': None, '__annotations__': {}, '__builtins__': <module at remote 0x7ffff6ea7180>}, locals={'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': <type at remote 0x555555b0eed0>, '__spec__': None, '__annotations__': {}, '__builtins__': <module at remote 0x7ffff6ea7180>}) at Python/ceval.c:662
#9  run_eval_code_obj () at Python/pythonrun.c:1078
#10 run_mod () at Python/pythonrun.c:1100
#11 PyRun_StringFlags () at Python/pythonrun.c:987
#12 PyRun_SimpleStringFlags () at Python/pythonrun.c:461
#13 pymain_run_command (cf=, command=<optimized out>) at Modules/main.c:241
#14 pymain_run_python (exitcode=) at Modules/main.c:522
#15 _Py_RunMain () at Modules/main.c:610
#16 pymain_main () at Modules/main.c:640
#17 _Py_UnixMain (argc=<optimized out>, argv=<optimized out>) at Modules/main.c:664
#18 __libc_start_main (main=<main>, argc=7, argv=, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=) at ../csu/libc-start.c:291
#19 _start ()