Add str() support to LineMatcher

[mcsitter]

Added __str__ method to LineMatcher class.

The LineMatcher class is used in the RunResult class, which has the stdout attribute, which is an instance of LineMatcher. result.stdout.str() is used 66 times in the codebase. The use of the str() function is mentioned here as well. If I should make any other changes. Since .str() is used throughout the codebase, changing everything to str(matcher) seems pointless.

If you think a test should be added, let me now, however it is implicitly tested in the Pytester tests.

• Create a new changelog file in the changelog folder, with a name like <ISSUE NUMBER>.<TYPE>.rst.

Closes #1265

[bluetech]

Thanks @mcsitter, I left some comments.

We should also update this sentence to refer to str(...) instead of .str() IMO: https://docs.pytest.org/en/latest/reference.html#pytest.pytester.RunResult.stdout

[mcsitter]

Thanks for the feedback! Not much to discuss about the requested changes.

I will try to formulate better changelog entries in the future and make myself more familiar with sphinx directives. Is there a sensible guideline for when to use them? There seem to be so many, that it could clutter up things quite a bit.

What would you put instead of :func:`stdout.str() <LineMatcher.str()>` ? I figure that is the part that needs to change.
:func:`str(stdout) <LineMatcher.__str__()>` ? Would that reference work?

[bluetech]

Is there a sensible guideline for when to use them? There seem to be so many, that it could clutter up things quite a bit.

I like hyperlinks so I tend to add them when someone might be inclined to follow them. But there are not strict guidelines, just depends on personal preference and laziness :)

What would you put instead of :func:stdout.str() <LineMatcher.str()> ? I figure that is the part that needs to change.
:func:str(stdout) <LineMatcher.__str__()> ? Would that reference work?

Right, I think that's the correct incantation, but only sphinx can tell :)

BTW in the Checks section of every PR there is a docs/readthedocs.org:pytest link to the rendered docs, so you can check that the reference works even without testing locally if you prefer.

[nicoddemus]

If you think a test should be added, let me now, however it is implicitly tested in the Pytester tests.

I really think a test is needed, mostly to ensure we don't regress this in the future by accident.

[mcsitter]

1. I updated the reference. Have a look at it here.

2. I added a test.

[nicoddemus]

LGTM!