Segmentation fault if built extension is located in sys_paths

Nobody has claimed this yet.

If one of the entries in sys_paths contain a built extension, and it is imported, the binary always seg faults. e.g. scandir in repl mode

```gdb
#0 0x00007ffff700cab8 in PyModule_Create2 () from /usr/lib64/libpython3.7m.so.1.0
#1 0x00007ffff7f82503 in PyInit__scandir () from /usr/lib64/python3.7/site-packages/_scandir.cpython-37m-x86_64-linux-gnu.so
#2 0x0000555555803896 in _PyImport_LoadDynamicModuleWithSpec (
spec=, origin='/usr/lib64/python3.7/site-packages/_scandir.cpython-37m-x86_64-linux-gnu.so', loader_state=None, submodule_search_locations=None, _set_fileattr=True, _cached=None) at remote 0x7ffff72c2190>, fp=) at ./Python/importdl.c:159
#3 0x0000555555803327 in _imp_create_dynamic_impl (module=,
spec=, origin='/usr/lib64/python3.7/site-packages/_scandir.cpython-37m-x86_64-linux-gnu.so', loader_state=None, submodule_search_locations=None, _set_fileattr=True, _cached=None) at remote 0x7ffff72c2190>, file=) at Python/import.c:2170
#4 _imp_create_dynamic (module=, args=, nargs=) at Python/clinic/import.c.h:289
#5 0x00005555557406eb in _PyMethodDef_RawFastCallDict (method=0x55555a2a0d80 , self=, args=0x7ffff72b74e8, nargs=1, kwargs={})
at Objects/call.c:530
#6 0x00005555557401b4 in _PyCFunction_FastCallDict (func=, args=0x7ffff72b74e8, nargs=33, kwargs={})
at Objects/call.c:586
#7 PyCFunction_Call (func=, args=, kwargs={}) at Objects/call.c:791
#8 0x00005555557d73f2 in do_call_core (func=,
callargs=(, origin='/usr/lib64/python3.7/site-packages/_scandir.cpython-37m-x86_64-linux-gnu.so', loader_state=None, submodule_search_locations=None, _set_fileattr=True, _cached=None) at remote 0x7ffff72c2190>,), kwdict=) at Python/ceval.c:4641
#9 _PyEval_EvalFrameDefault (
f=Frame 0x7ffff736ae50, for file , line 219, in _call_with_frames_removed (f=, args=(, origin='/usr/lib64/python3.7/site-packages/_scandir.cpython-37m-x86_64-linux-gnu.so', loader_state=None, submodule_search_locations=None, _set_fileattr=True, _cached=None) at remote 0x7ffff72c2190>,), kwds={}), throwflag=) at Python/ceval.c:3191
#10 0x00005555557da8dd in PyEval_EvalFrameEx (f=, throwflag=0) at Python/ceval.c:547
#11 _PyEval_EvalCodeWithName (_co=, globals=, locals=, args=, argcount=2, kwnames=0x0, kwargs=0x7ffff792bac0, kwcount=0, kwstep=1,
defs=0x0, defcount=0, kwdefs=0x0, closure=0x0, name='_call_with_frames_removed', qualname='_call_with_frames_removed') at Python/ceval.c:3930
#12 0x000055555573feb8 in _PyFunction_FastCallKeywords (func=, stack=0x21, nargs=0, kwnames=) at Objects/call.c:433
#13 0x00005555557d9b62 in call_function (pp_stack=0x7fffffff9a70, oparg=, kwnames=0x0) at Python/ceval.c:4616
#14 0x00005555557d7002 in _PyEval_EvalFrameDefault (
f=Frame 0x7ffff792b920, for file , line 1043, in create_module (self=, spec=, origin='/usr/lib64/python3.7/site-packages/_scandir.cpython-37m-x86_64-linux-gnu.so', loader_state=None, submodule_search_locations=None, _set_fileattr=True, _cached=None) at remote 0x7ffff72c2190>), throwflag=) at Python/ceval.c:3093
#15 0x00005555557403df in function_code_fastcall (co=, args=, nargs=, globals=) at Objects/call.c:283
#16 0x00005555557d9b62 in call_function (pp_stack=0x7fffffff9c60, oparg=, kwnames=0x0) at Python/ceval.c:4616
#17 0x00005555557d6fec in _PyEval_EvalFrameDefault (
f=Frame 0x7ffff739d750, for file , line 583, in module_from_spec (spec=, origin='/usr/lib64/python3.7/site-packages/_scandir.cpython-37m-x86_64-linux-gnu.so', loader_state=None, submodule_search_locations=None, _set_fileattr=True, _cached=None) at remote 0x7ffff72c2190>, module=None), throwflag=) at Python/ceval.c:3110
#18 0x00005555557403df in function_code_fastcall (co=, args=, nargs=, globals=) at Objects/call.c:283
#19 0x00005555557d9b62 in call_function (pp_stack=0x7fffffff9eb0, oparg=, kwnames=0x0) at Python/ceval.c:4616
#20 0x00005555557d708e in _PyEval_EvalFrameDefault (
f=Frame 0x7ffff72b8050, for file , line 670, in _load_unlocked (spec=, origin='/usr/lib64/python3.7/site-packages/_scandir.cpython-37m-x86_64-linux-gnu.so', loader_state=None, submodule_search_locations=None, _set_fileattr=True, _cached=None) at remote 0x7ffff72c2190>), throwflag=) at Python/ceval.c:3124
#21 0x00005555557403df in function_code_fastcall (co=, args=, nargs=, globals=) at Objects/call.c:283
#22 0x00005555557d9b62 in call_function (pp_stack=0x7fffffffa0a0, oparg=, kwnames=0x0) at Python/ceval.c:4616
#23 0x00005555557d708e in _PyEval_EvalFrameDefault (
f=Frame 0x7ffff792e8a0, for file , line 967, in _find_and_load_unlocked (name='_scandir', import_= for more, q to quit, c to continue without paging--
f7fbde30>, path=None, parent='', spec=, origin='/usr/lib64/python3.7/site-packages/_scandir.cpython-37m-x86_64-linux-gnu.so', loader_state=None, submodule_search_locations=None, _set_fileattr=True, _cached=None) at remote 0x7ffff72c2190>), throwflag=) at Python/ceval.c:3124
#24 0x00005555557403df in function_code_fastcall (co=, args=, nargs=, globals=) at Objects/call.c:283
#25 0x00005555557d9b62 in call_function (pp_stack=0x7fffffffa290, oparg=, kwnames=0x0) at Python/ceval.c:4616
#26 0x00005555557d708e in _PyEval_EvalFrameDefault (
f=Frame 0x7ffff728e650, for file , line 983, in _find_and_load (name='_scandir', import_=, module=), throwflag=) at Python/ceval.c:3124
#27 0x00005555557403df in function_code_fastcall (co=, args=, nargs=, globals=) at Objects/call.c:283
#28 0x0000555555741aae in object_vacall (callable=, vargs=0x7fffffffa3f0) at Objects/call.c:1202
#29 0x0000555555741b80 in _PyObject_CallMethodIdObjArgs (obj=, name=) at Objects/call.c:1252
#30 0x0000555555802301 in import_find_and_load (abs_name=) at Python/import.c:1648
#31 PyImport_ImportModuleLevelObject (name='_scandir', globals=, locals=, fromlist=None, level=0) at Python/import.c:1760
#32 0x00005555557d59eb in import_name (f=, name='_scandir', fromlist=None, level=0) at Python/ceval.c:4770
#33 _PyEval_EvalFrameDefault (f=Frame 0x7ffff78feda0, for file /usr/lib64/python3.7/site-packages/scandir.py, line 29, in (), throwflag=) at Python/ceval.c:2600
#34 0x00005555557da8dd in PyEval_EvalFrameEx (f=, throwflag=0) at Python/ceval.c:547
#35 _PyEval_EvalCodeWithName (_co=, globals=, locals=, args=, argcount=0, kwnames=0x0, kwargs=0x0, kwcount=0, kwstep=2, defs=0x0,
defcount=0, kwdefs=0x0, closure=0x0, name=0x0, qualname=0x0) at Python/ceval.c:3930
#36 0x00005555557d0cbf in PyEval_EvalCodeEx (_co=, globals=, locals=0x0, args=0x0, argcount=0, kws=0x0, kwcount=0, defs=0x0,
defcount=0, kwdefs=0x0, closure=0x0) at Python/ceval.c:3959
#37 PyEval_EvalCode (co=, globals=, locals=0x0) at Python/ceval.c:524
#38 0x00005555557ce27d in builtin_exec_impl (module=, source=,
globals={'__name__': 'scandir', '__doc__': 'scandir, a better directory iterator and faster os.walk(), now in the Python 3.5 stdlib\n\nscandir() is a generator version of os.listdir() that returns an\niterator over files in a directory, and also exposes the extra\ninformation most OSes provide while iterating files in a directory\n(such as type and stat information).\n\nThis module also includes a version of os.walk() that uses scandir()\nto speed it up significantly.\n\nSee README.md or https://github.com/benhoyt/scandir for rationale and\ndocs, or read PEP 471 (https://www.python.org/dev/peps/pep-0471/) for\nmore details on its inclusion into Python 3.5\n\nscandir is released under the new BSD 3-clause license. See\nLICENSE.txt for the full license text.\n', '__package__': '', '__loader__': , '__spec__': , origin='/usr/lib64/python3.7/site-packages/scandir.py', loa...(truncated),
locals={'__name__': 'scandir', '__doc__': 'scandir, a better directory iterator and faster os.walk(), now in the Python 3.5 stdlib\n\nscandir() is a generator version of os.listdir() that returns an\niterator over files in a directory, and also exposes the extra\ninformation most OSes provide while iterating files in a directory\n(such as type and stat information).\n\nThis module also includes a version of os.walk() that uses scandir()\nto speed it up significantly.\n\nSee README.md or https://github.com/benhoyt/scandir for rationale and\ndocs, or read PEP 471 (https://www.python.org/dev/peps/pep-0471/) for\nmore details on its inclusion into Python 3.5\n\nscandir is released under the new BSD 3-clause license. See\nLICENSE.txt for the full license text.\n', '__package__': '', '__loader__': , '__spec__': , origin='/usr/lib64/python3.7/site-packages/scandir.py', loa...(truncated)) at Python/bltinmodule.c:1079
#39 builtin_exec (module=, args=, nargs=) at Python/clinic/bltinmodule.c.h:283
#40 0x00005555557406eb in _PyMethodDef_RawFastCallDict (method=0x55555a29d5d0 , self=, args=0x7ffff7366b08, nargs=2, kwargs={})
at Objects/call.c:530
#41 0x00005555557401b4 in _PyCFunction_FastCallDict (func=, args=0x7ffff7366b08, nargs=33, kwargs={}) at Objects/call.c:586
#42 PyCFunction_Call (func=, args=, kwargs={}) at Objects/call.c:791
#43 0x00005555557d73f2 in do_call_core (func=,
callargs=(, {'__name__': 'scandir', '__doc__': 'scandir, a better directory iterator and faster os.walk(), now in the Python 3.5 stdlib\n\nscandir() is a generator version of os.listdir() that returns an\niterator over files in a directory, and also exposes the extra\ninformation most OSes provide while iterating files in a directory\n(such as type and stat information).\n\nThis module also includes a version of os.walk() that uses scandir()\nto speed it up significantly.\n\nSee README.md or https://github.com/benhoyt/scandir for rationale and\ndocs, or read PEP 471 (https://www.python.org/dev/peps/pep-0471/) for\nmore details on its inclusion into Python 3.5\n\nscandir is released under the new BSD 3-clause license. See\nLICENSE.txt for the full license text.\n', '__package__': '', '__loader__': , '__spec__': , origin='/usr/lib64/python...(truncated), kwdict=) at Python/ceval.c:4641
#44 _PyEval_EvalFrameDefault (
f=Frame 0x7ffff736a3d0, for file , line 219, in _call_with_frames_removed (f=, args=(, {'__name__': 'scandir', '__doc__': 'scandir, a better directory iterator and faster os.walk(), now in the Python 3.5 stdlib\n\nscandir() is a generator version of os.listdir() that returns an\niterator over files in a directory, and also exposes the extra\ninformation most OSes provide while iterating files in a directory\n(such as type and stat
\n\nThis module also includes a version of os.walk() that uses scandir()\nto speed it up significantly.\n\nSee README.md or https://github.com/benhoyt/scandir for rationale and\ndocs, or read PEP 471 (https://www.python.org/dev/peps/pep-0471/) for\nmore details on its inclusion into Python 3.5\n\nscandir is released under the new BSD 3-clause license. See\nLICENSE.txt for the full license text.\n', '__package__': '', '__loader__': ) at Python/ceval.c:3191
#45 0x00005555557da8dd in PyEval_EvalFrameEx (f=, throwflag=0) at Python/ceval.c:547
#46 _PyEval_EvalCodeWithName (_co=, globals=, locals=, args=, argcount=3, kwnames=0x0, kwargs=0x7ffff72ae3c8, kwcount=0, kwstep=1,
defs=0x0, defcount=0, kwdefs=0x0, closure=0x0, name='_call_with_frames_removed', qualname='_call_with_frames_removed') at Python/ceval.c:3930
#47 0x000055555573feb8 in _PyFunction_FastCallKeywords (func=, stack=0x21, nargs=0, kwnames=) at Objects/call.c:433
#48 0x00005555557d9b62 in call_function (pp_stack=0x7fffffffabd0, oparg=, kwnames=0x0) at Python/ceval.c:4616
#49 0x00005555557d7002 in _PyEval_EvalFrameDefault (
f=Frame 0x7ffff72ae220, for file , line 728, in exec_module (self=, module=, code=), throwflag=) at Python/ceval.c:3093
#50 0x00005555557403df in function_code_fastcall (co=, args=, nargs=, globals=) at Objects/call.c:283
#51 0x00005555557d9b62 in call_function (pp_stack=0x7fffffffadc0, oparg=, kwnames=0x0) at Python/ceval.c:4616
#52 0x00005555557d6fec in _PyEval_EvalFrameDefault (
f=Frame 0x7ffff73a3de0, for file , line 677, in _load_unlocked (spec=, origin='/usr/lib64/python3.7/site-packages/scandir.py', loader_state=None, submodule_search_locations=None, _set_fileattr=True, _cached='/usr/lib64/python3.7/site-packages/__pycache__/scandir.cpython-37.pyc', _initializing=True) at remote 0x7ffff7367b10>, module=),
throwflag=) at Python/ceval.c:3110
#53 0x00005555557403df in function_code_fastcall (co=, args=, nargs=, globals=) at Objects/call.c:283
#54 0x00005555557d9b62 in call_function (pp_stack=0x7fffffffb010, oparg=, kwnames=0x0) at Python/ceval.c:4616
#55 0x00005555557d708e in _PyEval_EvalFrameDefault (
f=Frame 0x7ffff78be120, for file , line 967, in _find_and_load_unlocked (name='scandir', import_=, path=None, parent='', spec=, origin='/usr/lib64/python3.7/site-packages/scandir.py', loader_state=None, submodule_search_locations=None, _set_fileattr=True, _cached='/usr/lib64/python3.7/site-packages/__pycache__/scandir.cpython-37.pyc', _initializing=True) at remote 0x7ffff7367b10>), throwflag=) at Python/ceval.c:3124
#56 0x00005555557403df in function_code_fastcall (co=, args=, nargs=, globals=) at Objects/call.c:283
#57 0x00005555557d9b62 in call_function (pp_stack=0x7fffffffb200, oparg=, kwnames=0x0) at Python/ceval.c:4616
#58 0x00005555557d708e in _PyEval_EvalFrameDefault (
f=Frame 0x7ffff731a050, for file , line 983, in _find_and_load (name='scandir', import_=, module=), throwflag=) at Python/ceval.c:3124
#59 0x00005555557403df in function_code_fastcall (co=, args=, nargs=, globals=) at Objects/call.c:283
#60 0x0000555555741aae in object_vacall (callable=, vargs=0x7fffffffb360) at Objects/call.c:1202
#61 0x0000555555741b80 in _PyObject_CallMethodIdObjArgs (obj=, name=) at Objects/call.c:1252
#62 0x0000555555802301 in import_find_and_load (abs_name=) at Python/import.c:1648
#63 PyImport_ImportModuleLevelObject (name='scandir', globals=, locals=, fromlist=None, level=0) at Python/import.c:1760
#64 0x00005555557d59eb in import_name (f=, name='scandir', fromlist=None, level=0) at Python/ceval.c:4770
#65 _PyEval_EvalFrameDefault (f=Frame 0x7ffff78baca0, for file , line 1, in (), throwflag=) at Python/ceval.c:2600
#66 0x00005555557da8dd in PyEval_EvalFrameEx (f=, throwflag=0) at Python/ceval.c:547
#67 _PyEval_EvalCodeWithName (_co=, globals=, locals=, args=, argcount=0, kwnames=0x0, kwargs=0x0, kwcount=0, kwstep=2, defs=0x0,
defcount=0, kwdefs=0x0, closure=0x0, name=0x0, qualname=0x0) at Python/ceval.c:3930
#68 0x00005555557d0cbf in PyEval_EvalCodeEx (_co=, globals=, locals=0x0, args=0x0, argcount=0, kws=0x0, kwcount=0, defs=0x0,
defcount=0, kwdefs=0x0, closure=0x0) at Python/ceval.c:3959
#69 PyEval_EvalCode (co=, globals=, locals=0x0) at Python/ceval.c:524
#70 0x000055555581431b in run_mod (mod=, filename=,
globals={'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': , '__spec__': None, '__annotations__': {}, '__builtins__': },
locals={'__name__': '__main__', '__doc__': None, '__package__': None, '__loader__': , '__spec__': None, '__annotations__': {}, '__builtins__': }, flags=, arena=) at Python/pythonrun.c:1035
#71 PyRun_InteractiveOneObjectEx (fp=, filename=, flags=) at Python/pythonrun.c:256
#72 0x0000555555813afe in PyRun_InteractiveLoopFlags (fp=0x55555a58c6e0, filename_str=, flags=0x7fffffffbad0) at Python/pythonrun.c:120
#73 0x00005555558139f8 in PyRun_AnyFileExFlags (fp=0x55555a58c6e0, filename=0x55555a592ce0 "", closeit=0, flags=0x7fffffffbad0) at Python/pythonrun.c:78
#74 0x00005555556f8b54 in pyembed::pyinterp::MainPythonInterpreter::run_repl (self=0x7fffffffc238) at pyembed/src/pyinterp.rs:739
#75 0x00005555556f57a0 in pyembed::pyinterp::MainPythonInterpreter::run (self=0x7fffffffc238) at pyembed/src/pyinterp.rs:525
#76 0x00005555556f67fc in pyembed::pyinterp::MainPythonInterpreter::run_and_handle_error (self=0x7fffffffc238) at pyembed/src/pyinterp.rs:617
#77 0x00005555556f6b47 in pyembed::pyinterp::MainPythonInterpreter::run_as_main (self=0x7fffffffc238) at pyembed/src/pyinterp.rs:654
#78 0x00005555556bb956 in requests_dec1::main () at src/main.rs:19
```

If it can not be fixed, maybe an `ImportError` can be raised instead.

Reproduce the crash in repl mode by importing the built scandir extension from sys_paths. Start with the Python import path shown in Python/importdl.c and the PyModule_Create2/PyInit__scandir frames, then isolate why this placement causes the segmentation fault. Done means the extension imports without a segfault in this scenario.

Written by the indexing model from the issue text.