…hained name lookups in _PyType_Lookup().

…m update_one_slot().

…r ceases to be a valid base type, there'll probably be larger code sections to change than this one.

…common in Python 3 now.

Also make the step from "return NULL" error handling to "goto error" reference cleanup explicit.

Distinguish between "error" and "error with exception" cases in _PyType_LookupUncached().
Fix a reference leak of "mro" on lookup errors.
Resolves issues found by Serhiy Storchaka.

…isting) API names.

Suggested by Serhiy Storchaka.

…l PyObject_GetItem() for them.

…e-calculation if the mapping is not exactly a dict.

…ential re-calculation if the mapping is not exactly a dict."

This reverts commit 1d52082.

… and call PyObject_GetItem() for them."

This reverts commit 09e716a.

…g lookup exceptions, just like "_PyType_Lookup()" did previously.

…ce eating lookup exceptions, just like "_PyType_Lookup()" did previously."

This reverts commit 4efde8e.

…) from functions that swallow live exceptions.

…rywhere else).

… handle them in the code that calls these functions.

The one non-exception error case during lookup ("no MRO") is not handled since it is unlikely and not user visible.
Note that this changes the signature of both functions, but they are clearly not public functions.
Currently leads to crashes due to NULL returns without exceptions set. Needs investigation.