When Aifc_read runs initfp, it conditionally sets self._ssnd_chunk and is not guaranteed to do so. At the bottom of the method, a check is made to see if the attribute has a false value; and if so, an error is supposed to be raised. If a SSND chunk is never found, checking self._ssnd_chunk causes an attribute error to be raised similar to this:

AttributeError: 'Aifc_read' object has no attribute '_ssnd_chunk'

The error was found on the following distribution:

Python 3.6.2 (v3.6.2:5fd33b5, Jul  8 2017, 04:57:36) [MSC v.1900 64 bit (AMD64)] on win32