Better differenciation between SSHException in PKey

[cybiere]

Hi,
I'm trying to identify whether an arbitrary file is (1) a SSH private key, (2) using which algo, (3) if it has a passphrase and if yes (4) if the passphrase I provide is valid.

I use a trial and error process basing myself on the exceptions raised, so if I need a passphrase I have paramiko.ssh_exception.PasswordRequiredException telling me so. If I try to load an ECDSA with paramiko.RSAKey.from_private_key_file, I have an paramiko.ssh_exception.SSHException. But if I try to load a RSA key with the same line using a wrong passphrase, I still have a SSHException, and I must check the string value of the exception to differenciate (if "checkints do not match" in str(e):)

It would be great to have for instance a paramiko.ssh_exception.InvalidPasswordException (raised in pkey.py line 477) so that people (at least I :D ) don't have to rely on parsing the error string :)