foo.py

import sys
import json
import traceback

import cherrypy


def handle_error():
	"""
	Handle unexpected errors (500).
	"""
	type, exc, tb = sys.exc_info()
	cherrypy.response.body = error_page(
		getattr(exc, 'status', 500),
		message=traceback.format_exception_only(type, exc),
		traceback=list(traceback.extract_tb(tb)),
	).encode('utf-8')


def error_page(status, message, traceback, version=None):
	"""
	Handle known errors (400), such as from HTTPError.
	"""
	cherrypy.response.status = status
	cherrypy.response.headers["Content-Type"] = "application/json"
	body = dict(
		message=message,
		traceback=_ensure_split(traceback),
		status=status,
	)
	return json.dumps(body, default=_handle_FrameSummary)


def _ensure_split(traceback):
	return traceback.split('\n') if isinstance(traceback, str) else traceback


def _handle_FrameSummary(ob):
	if isinstance(ob, traceback.FrameSummary):
		return tuple(ob)
	raise TypeError(ob)