all invocations of PyCObject_Check(pystate) should return a meaningful exception
all invocations of PyCObject_Check(pystate) should return a meaningful exception

without this we see:
 SystemError: error return without exception set
which is not very helpful

Fixes #281

git-svn-id: d5d2f0ec4d94f69790b3b7db0928a7621ad98150@3004 e27351fd-9f3e-4f54-a53b-843176b1656c

prashanthpai/PyKerberos,prashanthpai/PyKerberos,prashanthpai/PyKerberos