Re: datetime.date.fromisocalendar
Note that this now can throw OverflowError instead of ValueError when
using the C version of datetime. There is precedent for this, e.g.,
datetime.date.fromordinal will throw an OverflowError with the C module
but ValueError with the Python.
Also, prior to this PR, the C version fromisocalendar would throw a ValueError while the Python version throws TypeError for issues with e.g, missing arguments.

Two small notes:

1. Let me know if this diff size is too small and piece-meal-y!
2. I like the docstrings in Lib/datetime.py better, but unless otherwise told, I'll save that for another issue.

2. I like the docstrings in Lib/datetime.py better, but unless otherwise told, I'll save that for another issue.

Indeed, it's good to keep these Argument Clinic conversions as straightforward as possible.

Closing and re-opening to restart the hanged Travis-CI check.

Thanks, looks like everything's green :-)

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1. Let me know if this diff size is too small and piece-meal-y!

In my opinion this is fine, huge PRs can be hard to work with.

To respond to all points re. types of exceptions raised:

Note that this now can throw OverflowError instead of ValueError when using the C version of datetime.

As I stated above, I suggest keeping the behavior of raising ValueError rather than OverflowError.

There is precedent for this, e.g., datetime.date.fromordinal will throw an OverflowError with the C module but ValueError with the Python.

Changing this to raise ValueError instead of OverflowError would be an improvement IMO.

Also, prior to this PR, the C version fromisocalendar would throw a ValueError while the Python version throws TypeError for issues with e.g, missing arguments.

These inconsistencies are unfortunate, but relatively minor. If this PR fixes that, adding a test for it would be great!

@hauntsaninja could you fix merge conflicts, please?