Problem connecting via paramiko + kerberos

Currently, when I want to connect to a node, I just do: ssh username@node

and everything works fine. (thanks Kerberos :-)) Now I am trying to develop a simple python script that connects to a specified node, but I cannot connect to it using this script.
My next script:

import paramiko
import gssapi

ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())

ssh.connect(hostname = 'node_name', username = 'my_uname', gss_auth = True, gss_kex = True)

      

        
        
        
      

    

But I got this error:

paramiko.ssh_exception.AuthenticationException: Authentication failed.

      

        
        
        
      

    

I also tried

ssh.connect(hostname = 'node_name', username = 'my_uname', gss_auth = True, gss_kex = True, gss_deleg_creds=True)

      

        
        
        
      

    

and the resulting error changed slightly:

gssapi.error.GSSException: (131072) An invalid name was supplied. Minor code: (100001) Success. Target: node_name

      

        
        
        
      

    

Any suggestions? Thank!