For the same reasons as the runtime Python test, clean up the SDK test.
Also port from Python 2 to Python 3, as that's what is supported now.
(From OE-Core rev: bead742a3ffc0a53162fb0c36610d74a1422e7b3)
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>