Comment 1 for bug 1844822

msgpack is actually included as a requirement of oslo.privsep, with the following requirement:

msgpack>=0.5.0 # Apache-2.0

From the changelog at https://github.com/msgpack/msgpack-python/blob/master/ChangeLog.rst it looks like max_bin_len was removed in 0.6.1, so perhaps there needs to be a limit set the version.

Will re-assign to oslo.privsep for further investigation.