Pin testtools to avoid breakage in 0.9.35
Pin testtools to avoid breakage in 0.9.35

Change-Id: Ieb023fcb437191f3e3a8fb80d5ed15c2f5611b6b
Signed-off-by: Paul Belanger <b4265d8fef626f73eff739ef4ffce9d45b30eddd@polybeacon.com>

kickstandproject/python-payloadclient