Don't install msgpack 0.5.5
Don't install msgpack 0.5.5

This version has known critical issues.

See https://github.com/msgpack/msgpack-python/commit/da902f9c1d996fb461f1efef6487ef40d32d365a#r27725642
for more information.

saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt,saltstack/salt