BadAuthenticationType or SSHException when no authentication method needed

I believe this issue may be related to #787.

Basically, although OpenSSH's client succeeds:

debug1: Authentication succeeded (none).

Trying to connect with Paramiko either with generic password or None as password does not work.

I think that None and disabling key based authentication should work, indicating to the client library that no authentication method is the expected.

>>> ssh.connect(hostname='', username='root', password='Password', port=48409, timeout=30, compress=True, look_for_keys=False, allow_agent=False, auth_timeout=30, banner_timeout=30)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.7/site-packages/paramiko/client.py", line 437, in connect
    passphrase,
  File "/usr/local/lib/python3.7/site-packages/paramiko/client.py", line 749, in _auth
    raise saved_exception
  File "/usr/local/lib/python3.7/site-packages/paramiko/client.py", line 736, in _auth
    self._transport.auth_password(username, password)
  File "/usr/local/lib/python3.7/site-packages/paramiko/transport.py", line 1436, in auth_password
    return self.auth_handler.wait_for_response(my_event)
  File "/usr/local/lib/python3.7/site-packages/paramiko/auth_handler.py", line 250, in wait_for_response
    raise e
paramiko.ssh_exception.BadAuthenticationType: ('Bad authentication type', ['']) (allowed_types=[''])

>>> ssh.connect(hostname='', username='root', password=None, port=48409, timeout=30, compress=True, look_for_keys=False, allow_agent=False, auth_timeout=30, banner_timeout=30)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.7/site-packages/paramiko/client.py", line 437, in connect
    passphrase,
  File "/usr/local/lib/python3.7/site-packages/paramiko/client.py", line 750, in _auth
    raise SSHException("No authentication methods available")
paramiko.ssh_exception.SSHException: No authentication methods available

Start with the authentication flow shown in paramiko/client.py, especially connect and _auth, then trace transport.py and auth_handler.py for auth_password and the no-method response. Reproduce the OpenSSH-style none-authentication case and verify that a connection succeeds when no password or key authentication is needed.