python3: fix imports compatibility

Python3 reorganized the standard library and moved several functions
to different modules. Six provides a consistent interface
to them through the fake six.moves module.

However, the urlparse, urllib2, etc modules have been combined
into one module which Six does not support so do it the old
fashioned way.

Change-Id: Ieb7cc7ee2a4a97807873cfe2fc3fa0a5cf3c3980
Signed-off-by: Chuck Short <chuck.short@canonical.com>