I am attempting to use the Putty SCP program to copy files to a server. I am launching it with a Python subprocess:
`subprocess.check_output(pscp + ' -r -l ' + self._properties['ssh user'] + ' -pw ' + self._properties['ssh password'] + ' -4 -batch ' + local_path + ' ' + self._properties['ssh user'] + '@' + self._properties['target ip'] + ':' + destination_dir)`

Which resolves correctly to the following command:
`pscp -r -l root -pw password -4 -batch projects\packages\controller-fw\build\packager\controller-fw-iMx6-release root@10.52.120.201:/root/temp`

What I am seeing is it abort the connection:

```
error   26-Apr-2019 14:35:28    The server's host key is not cached in the registry. You
error   26-Apr-2019 14:35:28    have no guarantee that the server is the computer you
error   26-Apr-2019 14:35:28    think it is.
error   26-Apr-2019 14:35:28    The server's ssh-ed25519 key fingerprint is:
error   26-Apr-2019 14:35:28    ssh-ed25519 255 b9:a3:75:d7:c5:73:68:37:5d:6c:d1:61:6f:57:b4:ab

```

Is there a way to automatically accept the SSH key stuff? I had hoped using the -batch option would resolve it, but all it does is make it abort. I have looked into preceding it with a `plink` call, but it isn't clear from the manual that it would behave any differently. Is there a correct way to do this? 

Just before people ask, I am switching away from Paramiko due to poor performance reasons. It takes > 5 minutes to upload files that FileZilla can do in 30 seconds.