ems:admin:login none existing user throws 500 error

[Davidmattei]

When running ems:admin:login --username=test --password=test we get a 500 error. This should just return a 400 invalid credentials. Not a 404 we do not want to guess on usernames.

[theus77]

I tried with the branch 5.18 and it returns a 401 Unauthorized:

Admin - login
=============

[info] Request: "POST http://localhost:8881/auth-token"
[info] Response: "401 http://localhost:8881/auth-token"
                                                                                                                        
 [ERROR] Invalid credentials!                                                                       

Looks good to me