NovaException: Unexpected vif_type=binding_failed In Openstack Juno Migration

Sample Error
=============
ERROR nova.compute.manager [req-] [instance: ******-******-******-*******] Setting instance vm_state to ERROR
TRACE nova.compute.manager [instance: ******-******-******-*******] Traceback (most recent call last):
TRACE nova.compute.manager [instance: ******-******-******-*******]   File "/usr/lib/python2.7/site-packages/nova/compute/manager.py", line 5596, in _error_out_instance_on_exception
TRACE nova.compute.manager [instance: ******-******-******-*******]     yield
TRACE nova.compute.manager [instance: ******-******-******-*******]   File "/usr/lib/python2.7/site-packages/nova/compute/manager.py", line 3459, in resize_instance
TRACE nova.compute.manager [instance: ******-******-******-*******]     block_device_info)
TRACE nova.compute.manager [instance: ******-******-******-*******]   File "/usr/lib/python2.7/site-packages/nova/virt/libvirt/driver.py", line 4980, in migrate_disk_and_power_off
TRACE nova.compute.manager [instance: ******-******-******-*******]     utils.execute('ssh', dest, 'mkdir', '-p', inst_base)
TRACE nova.compute.manager [instance: ******-******-******-*******]   File "/usr/lib/python2.7/site-packages/nova/utils.py", line 165, in execute
TRACE nova.compute.manager [instance: ******-******-******-*******]     return processutils.execute(*cmd, **kwargs)
TRACE nova.compute.manager [instance: ******-******-******-*******]   File "/usr/lib/python2.7/site-packages/nova/openstack/common/processutils.py", line 193, in execute
TRACE nova.compute.manager [instance: ******-******-******-*******]     cmd=' '.join(cmd))
TRACE nova.compute.manager [instance: ******-******-******-*******] ProcessExecutionError: Unexpected error while running command.
TRACE nova.compute.manager [instance: ******-******-******-*******] Command: ssh 10.5.2.20 mkdir -p /var/lib/nova/instances/******-******-******-*******
TRACE nova.compute.manager [instance: ******-******-******-*******] Exit code: 255
TRACE nova.compute.manager [instance: ******-******-******-*******] Stdout: ''
TRACE nova.compute.manager [instance: ******-******-******-*******] Stderr: 'Host key verification failed.\r\n'
TRACE nova.compute.manager [instance: ******-******-******-*******]
ERROR oslo.messaging.rpc.dispatcher [-] Exception during message handling: Unexpected error while running command.
Command: ssh 10.5.2.20 mkdir -p /var/lib/nova/instances/******-******-******-*******
Exit code: 255
Stdout: ''
Stderr: 'Host key verification failed.\r\n'

Things Need to be checked

Configure the nova user
First things first, let's make sure our nova user has an appropriate shell set:

cat /etc/passwd | grep nova
Verify that the last entry is /bin/bash.

If not, let's modify the user and make it so:

usermod -s /bin/bash nova


After doing this the next steps are all run as the nova user.
SSH Configuration
su - nova
We need to generate an SSH key:

ssh-keygen

Next up we need to configure SSH to not do host key verification, unless you want to manually SSH to all compute nodes that exist and accept the key (and continue to do so for each new compute node you add).

cat << EOF > ~/.ssh/config
Host *
    StrictHostKeyChecking no
    UserKnownHostsFile=/dev/null
EOF

Make Password less Authentication with all Nova user's.