Implement SSH authentication exception error for

[sawu-juniper]

Hi Nitin,

As discussed, I raise this gitHub issue to implement the requested exception on SSH -

Need to implement following in PyEZ exception error to handle the SSH key authentication failure.

except paramiko.BadHostKeyException as e:
    raise Exception('BadHostKeyException on ' + hostname)
except paramiko.AuthenticationException as e:
    raise Exception('AuthenticationException on ' + hostname)
except paramiko.SSHException as e:
    raise Exception('SSHException on ' + hostname)

Thanks and Regards,
Sanming