RFC: Starred arg/kwarg unpacking in Assert rewrites

• a detailed description of the bug or suggestion
• output of pip list from the virtual environment you are using
• pytest and operating system versions
• minimal example if possible

Right now, unpacked arguments render like so:

>           assert f(*args) == expected
E           assert False == True
E            +  where False = <function ...>(*([4, 2, 3, 0, 3, 1, ...], 0))

This would be more readable if the argument tuple were unpacked like so:

E            +  where False = <function ...>([4, 2, 3, 0, 3, 1, ...], 0)

Something similar could apply to keyword arguments, though that may prove trickier: more edge cases.

Notes from preliminary hacking on visit_Assert, etc:

• The "trivial" cases of List/Tuple/Dict literal unpacking aren't too bad
• May require some codegen to handle formatting – ', '.join(args), but handling termwidth
• Unpacking calls with multiple starred expressions will be confusing – fallback to existing path

No guarantees as to if I'll take this up – certainly not until mid-September at the earliest – but the idea's written up for myself (or someone else) to implement later.

Start with the preliminary work around visit_Assert and the existing assertion-rewrite rendering path. Determine how literal starred positional arguments should be formatted, including term width and multiple starred expressions, and assess the additional keyword-argument edge cases. Done means readable unpacked output with a defined fallback for confusing cases.