fix failing doc test

Author: tusharsadhwani

Doc/conf.py

@@ -259,6 +259,7 @@
     ('c:data', 'PyExc_UnicodeEncodeError'),
     ('c:data', 'PyExc_UnicodeError'),
     ('c:data', 'PyExc_UnicodeTranslateError'),
+    ('c:data', 'PyExc_UnpackError'),
     ('c:data', 'PyExc_ValueError'),
     ('c:data', 'PyExc_ZeroDivisionError'),
     # C API: Standard Python warning classes