When running cPickle in restricted mode, the module tries to import
copyreg which does not appear to exist anywhere.  The problem is in
cPickle.c 

 2980 	if (PyEval_GetRestricted()) {
 2981 		/* Restricted execution, get private tables */
 2982 		PyObject *m = PyImport_Import(copyreg_str);
 2983 
 2984 		if (m == NULL)
 2985 			goto err;
 2986 		self->dispatch_table = PyObject_GetAttr(m, dispatch_table_str);
 2987 		Py_DECREF(m);
 2988 		if (self->dispatch_table == NULL)
 2989 			goto err;
 2990 	}
 2991 	else {
 2992 		self->dispatch_table = dispatch_table;
 2993 		Py_INCREF(dispatch_table);
 2994 	}

copyreg_str should probably be copy_reg_str