> I think modern editors are expected to have this sort of functionality
> built into them [1].

Mine doesn't :)

> XCode is simply amazing where it will pop up errors and quote the C99
> standard [2].

That's a standard though, the ones in PEP8 are just conventions/guidelines/suggestions.

> We don't expect IDLE to have all that functionality but it seemed to
> us like it would be great to add pep8 or PyFlakes to IDLE.

AFAIU PyFlakes should be able to catch actual problems with the code -- not just simply suggesting a particular style -- so it would be a better candidate.

> It is possible we could create an extension but that would void
> Python's motto "batteries included".

Often editors are able to download extensions automatically from a central place, without having to ship them all by default.  Doing this is probably more work though, but on the other hand it would be more flexible.

> In addition tools like pep8 and PyFlakes could be useful for other purposes as well.

Are you suggesting to include it directly in the stdlib, and not as part of IDLE?

> JayKrish is checking with the authors of pep8 about license issues.

Note that that's not the only issue.  Even if the license is OK, before inclusion we would have to make sure that the module meets the quality standards for the repo and that the author is still active and willing to maintain it for at least a few years in the CPython repo.  A PEP would likely be required, especially if the module gets included directly in the stdlib (as opposed as including it just in IDLE).  This also means that external development of the module should stop and move to the stdlib, and follow the release schedule of Python instead of release whenever they want (in theory they could maintain both, but it's more work).