There are already plenty RPC libraries for Python. Many of them mature, tested and with an active community behind. So why build yet another one?
We discovered that most of those libraries make the assumption that they're running within a trusted network; that a client/server architecture means clients connect and consume resources exposed by the server and not vice versa.
RESTful APIs are great to consume them in the browser or in a simple client/server architecture. Once you add more distributed components and services to the game, running on potentially hostile networks, the common HTTP/RESTful design pattern becomes less practical. With pseud we can get over these limitations by providing secure, fault-tolerant, RPC style communication built for fast and easy machine to machine communication.
Also thanks to the ZCA, pseud comes with a pluggable architecture that allows easy integration within your existing stack. It is usable within any web application (Django, Flask, aiohttp, sanic, Pyramid, Tornado, ...).