@MonishKumar Could you provide the entire exception ?

From the one line error message, I suspect this is due to the SSL cipher suites required by the SFTP server is not available on cluster. 

You can run below to get the cipher suites that sftp required:

%sh
sudo apt-get -y install nmap
nmap --script ssl-enum-ciphers -p 22 20.118.190.31