Between gofer 1.4 and 2.x, support for python-amqplib was discontinued. The pulp documentation for 2.6 indicates that for rabbit, users need to install python-gofer-amqp (instead) but the release notes don't mention this for upgrades.
https://github.com/pulp/pulp/pull/1607
2.6.0-0.7.beta
A note was added to docs/user-guide/release-notes/2.6.x.rst
Moved to https://pulp.plan.io/issues/677