Require requests[security] for cb6 to work

[brianebeyer]

No description provided.

[jgarman]

What versions of python does this fail on? I just tested with Python 2.6.6 on CentOS 6 (the oldest we support) and it worked with "plain" requests - albeit with warnings to a Cb Response 6.1.0.170405.0957 server.

Adding [security] does require you to install several C libraries which makes life more difficult- but if we can't connect at all under certain circumstances, then obviously we have to bite the bullet and document the changes for those running ancient versions of python.

[brianebeyer]

Mac 10.12.4, standard Python 2.7.10

Without 'requests[security]', it fails to connect every time. We used this link (https://github.com/kennethreitz/requests/issues/3189) to lead us to the solution.

[jgarman]

OK thanks - I'll add some text around how to install the devel libraries required to build the ffi and cryptography python modules and test on Windows.