py3: Resolve unicode issues

py3: Resolve unicode issues

Python 3 is unicode only. While many of the issues with unicode, such
as the now invalid 'u' prefix, have already been resolved, there are a
few more issues.

Many of these issues are related to HTTPResponse.content, which returns
bytes and needs to be "decoded" in order to perform actions like
concatenation with str objects (unicode). Where possible, make use of
assertContains, per the Django documentation (http://bit.ly/1lRDYie),
else fall back to including a 'decode' statement.

Signed-off-by: Stephen Finucane <stephen.finucane@intel.com>