Merged requested to merge bitbucket/merged-pr-212 into branch/default
Created originally on Bitbucket by msabramo (Marc Abramowitz)
Was already merged in Bitbucket before import, marked as merged by the import user
filename == NULL works.
A prelude to refactoring
PyErr_SetFromErrnoWithFilename to use
PyErr_SetFromErrnoWithFilenameObject which was just added in PR #211 (closed).