Kerberos follow-up

[offa]

Some open issues mentioned in #353 fixed:

1. Exception if kerberos is used but not installed
2. Tox config updated to include the extra dependency
3. Note added to the documentation. Is this enough or is a full pip call more suitable?

[offa]

The installation of optional dependencies through the pypi package doesn't work.

> pip install atlassian-python-api[kerberos]

Results in No matches found.

It works from source and the installed package contains some sort of dependency information (requires.txt) 🤔 :

requests
six
oauthlib
requests_oauthlib

[kerberos]

[kerberos:platform_system != "Windows"]
kerberos

[kerberos:platform_system == "Windows"]
kerberos-sspi

[offa]

Well … quotes to the trick:

pip install "atlassian-python-api[kerberos]"

And it works! 👍

[offa]

There's just on minor issue left: How to handle the requirements.txt?

1. Move kerberos to a seperate one which sources the common file
2. Keep all dependencies in one file as it's at the moment

Are there any preferences?

[gonchik]

I think the better way is keep in one file, as we can number of dependency.

[offa]

So, then the PR is ready from my side.

[gonchik]

Thank you :)