Most of changes are straightforward. Just replaced PyDict_GetItem*() with PyDict_GetItem*WithError() and added the check for PyErr_Occurred(). PyDict_GetItemString() with constant argument was replaced with _PyDict_GetItemIdWithError() for performance.

Some code was left unchanged. This was mostly in files where errors are very and error checking is not performed or errors are silenced in any case (Python/compile.c, Python/symtable.c, Objects/structseq.c, etc). These cases needed separate issues.

The most non-trivial change is in Objects/typeobject.c. The check for duplicated descriptors (in add_methods(), add_members() and add_getset()) was moved after creating the descriptor object. This improves performance by avoiding to create a temporary string objects. Duplicate descriptor names is a very uncommon case -- there were only two cases in the stdlib (besides tests), and one of them already is fixed (PR 11053).