throwing errors from within errorhandlers with flask

gistfile1.py

from flask import Flask, abort

app = Flask(__name__)

@app.route('/')
def foo():
    abort(403)
    return 'this wont ever be returned'

@app.errorhandler(403)
def foo(x):
    # here we throw an exception inside an error handler
    abort(404) 
    return 'this wont ever be returned'

@app.errorhandler(404)
def foo(x):
    return 'im the 404 handler'

@app.errorhandler(500)
def foo(err):
    # check here for a 500 to avoid an infinite loop
    return app.handle_user_exception(err)


with app.test_client() as c:
    assert c.get('/').data == 'im the 404 handler'