Created originally on Bitbucket by msabramo (Marc Abramowitz)
Was already merged in Bitbucket before import, marked as merged by the import user
This adds function PyErr_SetFromErrnoWithFilenameObject
(which exists in the CPython C API) to cpyext.
This fixes the following bug: https://bugs.pypy.org/issue991
This supersedes https://bitbucket.org/pypy/pypy/pull-request/208/add-pyerr_setfromerrnowithfilenameobject/diff