Test that generated notebook conform to black, isort and pylint

[lukany]

Black, isort and pylint are used to enforce code style in edvart. However, there is no code style check for generated code by edvart. This could be added to edvart's tests.

See below for an example how to check generated code via black:

import tempfile
import nbformat as nbf

from black import Mode, format_file_contents

handle, file = tempfile.mkstemp(suffix='.ipynb')
nbf.write(nb, file)

with open(file, "rw") as f:
    format_file_contents(f.read(), fast=False, mode=Mode())