ssh-keygen -t rsa -N "" -f my.key

sp.check_call(["ssh-keygen, "-t", "rsa", "-N", """", "-f", "my.key"])

sp.check_call(["ssh-keygen, "-t", "rsa", "-N", "''", "-f", "my.key"])

Saving key "my.key" failed: passphrase is too short (minimum five characters)

sp.check_call(["ssh-keygen", "-t", "rsa", "-N", "", "-f", "my.key"])