Use botocore vendoring of six

[kyleknap]

So I switched the CLI off of six to use botocore's version of six.

There is an interesting scenario for our vendored version of six where if you do something like:

from awscli.compat import six
from six.moves import shlex_quote

It will try to pull it from the six installed from dateutil which is a dependency of botocore. So, avoid doing that style of importing modules and functions from the vendored six.

Instead, we need to be explicit in how we import modules from six. Currently, something like this is totally fine:

from awscli.compat import six

if six.PY3:
   #some code

But this is not:

from awscli.compat import six
from six import PY3

if PY3:
   #some code

If you ever want to do it of the style of the second one refer to the compat.py file and add the import there if it is not located there. So, In the new format, if you want to import shlex_quote, you would add it to compat.py and do:

from awscli.compat import shlex_quote

I did my best to try to catch all of them. But, I may have missed some. I expect I missed a few in botocore. So if you run across one please fix it in both botocore and the cli.

cc @jamesls @danielgtaylor

[kyleknap]

I forgot:

Fixes #1051

[jamesls]

[danielgtaylor]

LGTM 🚢-it. I ran into this in the past as well. This format works too:

from awscli.compat import six

shlex_quote = six.moves.shlex_quote

It's a bit more verbose but can also go up with the imports. Anyway just pulling all these into the compat file seems like a decent approach to me.