Example:
---
from ctypes import c_int, CFUNCTYPE

def func():
    return (1, 2, 3)

cb = CFUNCTYPE(c_int)(func)
cb()
---

Output:
---
Traceback (most recent call last):
  File "_ctypes/callbacks.c", line 262, in 'converting callback result'
TypeError: an integer is required (got type tuple)
Exception ignored in: <function func at 0x7f0c267ff1f0>
---

Assertion error in debug mode:
---
Traceback (most recent call last):
  File "_ctypes/callbacks.c", line 262, in 'converting callback result'
TypeError: 'tuple' object cannot be interpreted as an integer
python: Python/errors.c:1435: _PyErr_WriteUnraisableMsg: Assertion `exc_type != NULL' failed.
Abandon (core dumped)
---

Attached PR fix the issue.