I am also getting same error in 2017 :)
and changing it to port 22 worked.
This is my standard script and netconf, ssh is enabled.
from jnpr.junos import Device
dev = Device(host='10.198.123.205',user='labs',password='labs1labs',port='22')
dev.open()
print dev.facts['version']
print dev.cli("show configuration system services")
dev.close()