How to use the pysftp.ConnectionException function in pysftp

else:
                params["password"] = self.sftp_password

            # not empty sftp_public_key means that we should verify sftp server with it
            cnopts = pysftp.CnOpts()
            if self.sftp_public_key:
                key = paramiko.RSAKey(data=base64.b64decode(self.sftp_public_key))
                cnopts.hostkeys.add(self.sftp_server, 'ssh-rsa', key)
            else:
                cnopts.hostkeys = None

            with pysftp.Connection(**params, cnopts=cnopts):
                raise exceptions.Warning(_("Connection Test Succeeded!"))

        except (pysftp.CredentialException,
                pysftp.ConnectionException,
                pysftp.SSHException):
            _logger.info("Connection Test Failed!", exc_info=True)
            raise exceptions.Warning(_("Connection Test Failed!"))

import pysftp
import paramiko
from globus import GLOBUSError
from spot import SPOTError
from newt import NEWTError
import ssh

__all__ = ['newt', 'spot', 'globus', 'sftp', 'ssh']

# Exceptions raised by clients that we care to handle
EXCEPTIONS = (pysftp.ConnectionException, paramiko.ssh_exception.BadAuthenticationType,
              paramiko.ssh_exception.AuthenticationException, GLOBUSError, SPOTError, GLOBUSError)