qpol.i: include filename info on policy file opening errors

Changes errors from this:

$ ./seinfo eggs
[Errno 2] No such file or directory

to this:

$ ./seinfo eggs
[Errno 2] No such file or directory: 'eggs'

setools/policyrep/qpol.i

@@ -185,7 +185,7 @@ typedef enum qpol_capability
     if (errno == EINVAL) {
         PyErr_SetString(PyExc_SyntaxError, "Invalid policy.");
     } else {
-        PyErr_SetFromErrno(PyExc_OSError);
+        PyErr_SetFromErrnoWithFilename(PyExc_OSError, arg1);
     }
     return NULL;
   }