add themysto_testing_utils to isort exceptions
add themysto_testing_utils to isort exceptions

original-commit-id: 12fbd68082bc6673f41bc5b270e33b7eee93286f
original-commit-url: https://github.com/ipython-contrib/IPython-notebook-extensions/commit/12fbd68082bc6673f41bc5b270e33b7eee93286f

jcb91/jupyter_nbextensions_configurator,jcb91/jupyter_nbextensions_configurator,jcb91/jupyter_nbextensions_configurator,jcb91/jupyter_nbextensions_configurator