With the z3/python web interface, if I ask:
x = Real (\'x\') solve(x * x == 2, show=True)
I nicely get:
Problem: [x·x = 2] Solu
Try your example with Z3 web interface, I get a result of sat.
sat
Z3 web interface and Z3Py are based on Z3 v4.0, so I think the problem is fixed in the upcoming release.