[issue38157] Add a recipe in unittest.mock examples about mock_open per file

[Karthikeyan Singaravelan]

Change by Karthikeyan Singaravelan <tir.karthi at gmail.com>:


----------
keywords: +patch
pull_requests: +15711
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/16090

_______________________________________
Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue38157>
_______________________________________