all curl's tests generated configuration and key files are fine, a real
connection is established to the test harness sftp server authenticating
and running a simple sftp remote pwd command.
The verification is done using OpenSSH's or SunSSH's sftp client tool with
a configuration file with the same options as the test harness socks server
with the exception that dynamic forwarding is not used for sftp.
Yang Tse
Daniel Stenberg