Use .rst as the file extension for reST-based PEPs

[brettcannon]

Requires not only renaming all relevant files but also updating code to accept the file extension. As part of this we can probably consider dropping the Content-Type as it will be known from the file extension (although others may disagree).

This will allow for rich rendering of the reST-based PEPS by GitHub.

[ncoghlan]

#32 covers supporting .rst as an extension in the Makefile and PEP 0 generator

[ncoghlan]

@berkerpeksag mentioned in #116 that the .rst extension isn't supported by the python.org importer yet.

I think that may be the only remaining barrier to a bulk rename of the existing text/x-rst PEPs.

[brettcannon]

That's been my assumption as well about where things stand.

[brettcannon]

This issue is also dependent on #4 .

[brettcannon]

Looks like www.python.org/dev/peps/ will now display PEPs with a .rst ending as demonstrated by PEP 550! The next problem is that the source link at the end of PEPs don't work for PEPs that end in .rst.

[berkerpeksag]

The problem is the converter doesn't know anything about the source file so we probably need to guess the extension (maybe do a HEAD request to .txt first; if status is not 200; try .rst?)

[brettcannon]

What I'm expecting is once #4 is done we can update the converter to assume .rst and then start moving all the file names over so it won't matter what the assumption is.

[gvanrossum]

Hm... The source link thing is sad. Where's the code for the converter?

[ncoghlan]

This is the offending line in the web app: https://github.com/python/pythondotorg/blob/master/peps/converters.py#L184

I'm thinking it may make sense to move that part out of the web app and into pep2html.py.