Remove python 2.4 and python 2.5 support.

As a project we do not support python 2.4 or python 2.5
and these versions of python are not tested, so remove
the compatibility code.

Change-Id: I267d9e7e83d85322c45d56d9c5256b514224ad8c
Signed-off-by: Chuck Short <chuck.short@canonical.com>