Don't use mock non-exist method assert_called_once

There isn't method assert_called_once of mock class
and hence does not really check anything. Let's use
assertEqual(1, mock.call_count) to check.

Change-Id: I2bdf62b775badc0adbe2c6f55bcc65cd13ac2d60
Refactor auth_token token cache members to class

The token cache members are moved from AuthToken to their own
class.

Change-Id: Ibf00d39435fa7a6d9a92a9bdfacc3f1b07f890ef
Session Documentation

Include some client documentation for how to work with a Session object.
This is generally high level with this expectation that a developer
could take the concepts found here and determine more from the module
documentation.

Change-Id: I5e44c1029ce160cb2798cfb8a535aa9f3311799a
Added help text for the debug option

This adds a short help text for --debug on the command line. Prior to
this short help text the debug option was hidden.

Change-Id: I2e641ec496e596fcc4879855ac750d957522be88
Closes-Bug: #1328813
Merge "Refactor auth_token token cache members to class"
Merge "Don't use mock non-exist method assert_called_once"
Merge "Session Documentation"
Using six.u('') instead of u''

In a few places, there's some u'' strings, this patch replaces
them by six.u(''), as this fixes things when running the unit
tests in Debian Wheezy.

Change-Id: I60c01f85901a33a0e3e7a255049084126558f031
auth_token _cache_get checks token expired

When auth_token stores the token in the cache, it's stored with
the expiration time; but when the token is retrieved from the
cache, if the expiration time has passed the token is treated as if
it wasn't cached. This creates extra work because now auth_token
has to check the token expiration (either by decrypting the PKI
token or online validation for UUID tokens).

With this change, getting the token from the cache will fail if the
expiration is past.

Change-Id: Id0ec6b3c2e5af4a2d910f16da4e0312733fc2198
Merge "Added help text for the debug option"
Merge "auth_token _cache_get checks token expired"
Updated from global requirements

Change-Id: I0804468699cd7af0b3b520c07fd0aeff809bd2b1