Switch to cmarkgfm completely for rendering Markdown

[theacodes]

Follow up to #67.

Towards pypa/packaging-problems#126

Note: There are wheels for cmarkgfm for basically everything but Python 2.7 on Windows. This is due to the hilariously ancient version of MSVC needed to compile the wheel and cmark just outright being uncompilable as-is. Basically, users of 2.7 on Windows will not be able to use readme_renderer at all. As long as we're okay with that, this can merge.

Wheels are available across Windows, Linux, and Mac for 2.7, 3.4, 3.5, and 3.6.

[theacodes]

@di alternatives for Windows 2.7 users include:

• Use a platform specifier for cmarkgfm and then warn them if they try to use it. (install succeeds, usage fails)
• Use a platform specifier for cmarkgfm, keep CommonMark as a fallback, work for CommonMark variant but fail for gfm variant.

[theacodes]

I'm a bit baffled as to how this change caused the txt tests to fail on 2.7. Weird.

[theacodes]

I'm a bit baffled as to how this change caused the txt tests to fail on 2.7. Weird.

Figured it out. CommonMark was pulling in future which cleverly provides html.escape which means that the branch in txt.py that checks for html.escape and falls back to cgi.escape was previously never used. Removing CommonMark removed future and thus html and made the previously unused branch trigger for 2.7 - which has different escape behavior for single quotes!

Fixed in 5e7c7d1 by just including future as a direct dependency and removing the problematic branch.

[anthrotype]

@jonparrott have you tried compiling the Windows 2.7 wheels using mingwpy toolchain?
https://anaconda.org/carlkl/mingwpy
https://github.com/mingwpy/mingwpy
https://mingwpy.github.io/

[theacodes]

@anthrotype nope, is there an easy way to do that with multibuild? I'm using that over in https://github.com/jonparrott/cmarkgfm-wheels.

[theacodes]

Aww it seems mingwpy is abandoned?

[anthrotype]

Aww it seems mingwpy is abandoned?

yes, but it still works for 2.7.
you can pip install -i https://pypi.anaconda.org/carlkl/simple/ mingwpy

I use it like this in another project where I need c++11 stuff not available for MSVC2008
https://github.com/googlei18n/compreffor/blob/master/.appveyor.yml
https://github.com/googlei18n/compreffor/blob/master/tox.ini#L4

[theacodes]

@anthrotype ah great. I've give that a shot this afternoon. Thank you!

[theacodes]

Thank you for the help @anthrotype! I got wheels working for Python 2.7 on Windows!

@di this should be good to go. :)