roslaunch SSH known_host errors - cannot launch remote nodes

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I am starting to use roslaunch across two systems (badmonkey and raspberrypi) running Indigo. I cannot seem to launch remote nodes and it appears to have something to do with SSH. I could use some help understanding how to isolate this issue. I currently have SSH public/private key authentication working in both directions (I can ssh user@system from either system with and without -p 22 to get to the other system with no password and it works great - I assume my respective user known_hosts file have been automatically updated per the ssh documentation). Is there something else I need to do with the system or user known_hosts file?

Here is the launch file:

<launch>
    <machine name="main-raspberry-pi" address="raspberrypi" default="true" user="pi"/>
    <machine name="badmonkey-machine" address="badmonkey" default="never" user="mike"/>

    <node pkg="inmoov" type="HandActionServer.py" name="inmoov_hand" machine="main-raspberry-pi" respawn="true" />
    <node pkg="inmoov" name="leap_motion_publisher" type="LeapPublisher.py" machine="badmonkey-machine" respawn="true" />
    <node pkg="inmoov" name="leap_motion_subscriber" type="LeapSubscriber.py" machine="main-raspberry-pi" respawn="true" />
</launch>

I use the this command:

roslaunch inmoov inmoov-rpi.launch --screen

When launching from the default system (raspberrypi) the remote node on badmonkey cannot be started:

... logging to /home/pi/.ros/log/abe119b2-7eb8-11e6-bc9a-b827eb200e86/roslaunch-raspberrypi-5384.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://raspberrypi:49070/
remote[badmonkey-0] starting roslaunch
remote[badmonkey-0]: creating ssh connection to badmonkey:22, user[mike]
remote[badmonkey-0]: failed to launch on badmonkey-machine:

Unable to establish ssh connection to [mike@badmonkey:22]: Server u'badmonkey' not found in known_hosts

[badmonkey-0] killing on exit
unable to start remote roslaunch child: badmonkey-0
The traceback for the exception was written to the log file

When launching from the non-default system (badmonkey) the remote node cannot be started:

... logging to /home/mike/.ros/log/525f5a1e-7eba-11e6-a2da-08002709c777/roslaunch-badmonkey-4440.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://badmonkey:40520/
remote[raspberrypi-0] starting roslaunch
remote[raspberrypi-0]: creating ssh connection to raspberrypi:22, user[pi]
remote[raspberrypi-0]: failed to launch on main-raspberry-pi:

raspberrypi is not in your SSH known_hosts file.

Please manually:
  ssh pi@raspberrypi

then try roslaunching again.

If you wish to configure roslaunch to automatically recognize unknown
hosts, please set the environment variable ROSLAUNCH_SSH_UNKNOWN=1

[raspberrypi-0] killing on exit
unable to start remote roslaunch child: raspberrypi-0
The traceback for the exception was written to the log file

When launching from the non-default system (badmonkey) with ROSLAUNCH_SSH_UNKNOWN=1 the remote node on raspberrypi cannot be started:

... logging to /home/mike/.ros/log/21bcad34-7eb6-11e6-9cb9-08002709c777/roslaunch-badmonkey-3649.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://badmonkey:43150/
remote[raspberrypi-0] starting roslaunch
remote[raspberrypi-0]: creating ssh connection to raspberrypi:22, user[pi]
remote[raspberrypi-0]: failed to launch on main-raspberry-pi:

Unable ...