Bug report

1. PyImport_GetImporter() can return NULL with set or not set error. The latter happens only ifsys.path_hooks orsys.path_importer_cache was deleted, or in more obscure cases: when string allocation for strings "path_hooks" or "path_importer_cache" fail, or thesys module was not yet created. These cases so obscure, that the user code most likely do not expect this. The only place wherePyImport_GetImporter() is used in Python itself expects an error to be set if NULL is returned.
2. PyImport_GetImporter() can crash (in debug build) or raise SystemError ifsys.path_hooks is not a list orsys.path_importer_cache is not a dict. Note that both are set to None in_PyImport_FiniExternal() (which is called inPy_FinalizeEx() andPy_EndInterpreter()).

Crash is unacceptable, so asserts should be replaced with runtime checks and raising an exception (RuntimeError looks suitable).

And I think thatPyImport_GetImporter() should set RuntimeError when it fails to getsys.path_hooks orsys.path_importer_cache. It is the most common error in similar cases.

Linked PRs

• gh-109521: Fix obscure cases handling in PyImport_GetImporter() #109522
• [3.12] gh-109521: Fix obscure cases handling in PyImport_GetImporter() (GH-109522) #109777
• [3.11] gh-109521: Fix obscure cases handling in PyImport_GetImporter() (GH-109522) #109781