Add betterssl extra

[sigmavirus24]

Fixes #1995

[kevinburke]

+1

[t-8ch]

Could we use another name which doesn't sound like it will solve all problems?

[dstufft]

So, I'm going to raise a question!

I was the one who opened the original ticket, but I wonder if it makes sense to do this anymore. On Python 3.4+ and Python 2.7.9+ it's not better anymore. On Python 3.2 and 3.3 it's better, but not in ways that couldn't be reproduced without extra dependencies.

Either way, this PR looks good to me, the only question is if we still need/want it just for Python 2.6 and Python <=2.7.8.

[sigmavirus24]

I don't think it will hurt to have it for 2.6 or <= 2.7.8.

[Lukasa]

I agree that it won't hurt us to have, but I agree with @t-8ch that we should avoid the slightly prejudicial name. Maybe just call it pyopenssl?

[sigmavirus24]

I really have no opinion on the name. I would think with_sni (i.e., pip install requests[with_sni] reads well) would be most descriptive of the use case for the largest number of users, but pyopenssl is fine too. I'll wait for @kennethreitz to decide.

[kennethreitz]

I'd rather give it a more generic/rememberable name.

security

[kennethreitz]

Updated to security. Now, let's document it!

[t-8ch]

I fear this generic and positive name will lead to people enabling it that don't need it. Triggering compilation of pyopenssl, breakage when missing development tools etc. And on Python3 it will be ignored anyways.

[kennethreitz]

@t-8ch false

[t-8ch]

urllib3 uses ndg-httpsclient. Importing this on py3 will raise a syntax error
and abort the import -> PyOpenSSL is not used.
In requests < 2.4.0 The syntax error will even bubble up and just crash
everything.

[kennethreitz]

we can fix that in setup.py

[t-8ch]

You mean: requests[betterssl] on Py3 will just be a noop?

[sigmavirus24]

@t-8ch I don't understand your concerns in this statement:

In requests < 2.4.0 The syntax error will even bubble up and just crash everything.

The extra does not ship with anything <= 2.4.0. How does this affect those people?

[t-8ch]

Just an example for downsides which can arise when using the pyopenssl backend