repro.py

import json
import os
import tempfile


def foo(filename):
    with open(filename, 'r') as file_obj:
        return file_obj.read()


def bar():
    filehandle, filename = tempfile.mkstemp()
    payload = {}
    os.close(filehandle)
    try:
        with open(filename, 'w') as file_obj:
            json.dump(payload, file_obj)
        return foo(filename)
    finally:
        os.remove(filename)


print(bar())