Correct way to load ecdsa keys with paramiko/pysftp with OpenSSH.. Solves issue: https://github.com/paramiko/paramiko/issues/350

pystfp_paramiko_ecdsa.py

#!/usr/bin/env python3

# This error is caused by using `paramiko.RSA()` to manually load an ecdsa key from your know_hosts file or for manually loading as bytes.
# Using: `key = paramiko.AgentKey()` instead seemingly detects the key type automatically and accepts the ecdsa-sha2-nistp256 key just fine.

# EXAMPLE: 

import pysftp
from base64 import decodebytes
import paramiko

hostname = "123.10.20.30"
password = "password123"
port = 2222
keydata = b"""BBBBE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBMGAGLpMKIeSkLkOizv78dfOVG+V2YGInryO/tPV3onFfUAm8zVHLfOIagbpqJI09UblO+ujSM+ZPN0ERnD6uSA="""

# LOAD THE ECDSA KEY
key = paramiko.AgentKey('ecdsa-sha2-nistp256', decodebytes(keydata))
# SET OPTS
cnopts = pysftp.CnOpts()
# ADD OUR KEY TO OPTS
cnopts.hostkeys.add(hostname, 'ecdsa-sha2-nistp256', key)
# CONNECT
with pysftp.Connection(hostname, port=port, username='root', password=password, cnopts=cnopts) as sftp:
    print("Connected!")
    with sftp.cd('/usr/share'):
        print("In remote /usr/share!")