There's some dead code in xmlparse_ParseFile() in Modules/pyexpat.c: the file pointer "fp" is always NULL, and as such the following code can never get entered into:

        if (fp) {
            bytes_read = fread(buf, sizeof(char), BUF_SIZE, fp);
            if (bytes_read < 0) {
                PyErr_SetFromErrno(PyExc_IOError);
                return NULL;
            }
        }

There might be similar situations in other methods.