[pkg] Set an upper bound to passlib We're using a deprecated API and are getting the following deprecation warning: :: the method passlib.context.CryptContext.encrypt() is deprecated as of Passlib 1.7, and will be removed in Passlib 2.0, use CryptContext.hash() instead. So let's make sure we're getting a working library. [ci skip]

debian/cubicweb-doc/html 
doc/book