Test: refactor format_docstring()

[erlend-aasland]

Based off of the warn-and-fail branch, hence the commit history. The new commit with the format_docstring() refactor is 7ff262e 9df8da9.

[erlend-aasland]

I realised that the format_docstring() helpers I introduced do not rely on self; how about moving the whole docstring formatting over to Function, and do it at render time?

[AlexWaygood]

I realised that the format_docstring() helpers I introduced do not rely on self; how about moving the whole docstring formatting over to Function, and do it at render time?

Makes sense to me!

[erlend-aasland]

It is weird that Function.render_parameters is a property. It is named and used as a method. It is also called twice for each function; if we move the docstring rendering to render_function, we only need to "call" render_parameters once.

[erlend-aasland]

python#107623 (first step)