Use Subprocess Runs for Example Tests

[Scienfitz]

runpy did not run example files in isolated environments, causing problems with examples that had hook modifications via monkeypatching. subprocess.run calls a separate process hence not exhibiting the problem

this also required some coverage exceptions as some utils are only tested in examples

[AdrianSosic]

Thanks! But it would be good if you could add an explanation both to the PR description AND in the code, so that people (including future us) don't wonder why this is necessary in the first place.

[Scienfitz]

@AdrianSosic there is explanation in the code?

[AdrianSosic]

@AdrianSosic there is explanation in the code?

Example of a comment that mostly restates the obvious, i.e. of the form

# Do X
X()

You:

# This runs it in a separate process
subprocess(...)

Doesn't answer why the separate environment is needed in the first place. Would be good to mention e.g. monkeypatching that is applied in the examples that breaks subsequent code execution or similar

[Scienfitz]

@AdrianSosic ping