The error: cannot resolve host address for machine ....

edit

I have installed the ROS in a raspberry 2. I use the code to set the environment .

source environment.sh

After that I make the roslaunch and there is an error code:

roslaunch duckietown joystick.launch veh:=wama

error:

cannot resolve host address for machine [wama]
The traceback for the exception was written to the log file

My URI is wama.local:11311

I changed the hostname to biecuole, and try to ping the biecuole and biecuole.local. They both work but the error is still existing

code:

roslaunch duckietown joystick.launch veh:=biecuole... logging to /home/robot2/.ros/log/f4462c94-c3f7-11e7-b0b6-74da38c7fa07/roslaunch-biecuole-8314.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://biecuole.local:32874/
remote[biecuole.local-0] starting roslaunch
remote[biecuole.local-0]: creating ssh connection to biecuole.local:22, user[zhang]
/usr/lib/python2.7/dist-packages/Crypto/Cipher/blockalgo.py:141: FutureWarning: CTR mode needs counter parameter, not IV
  self._cipher = factory.new(key, *args, **kwargs)
remote[biecuole.local-0]: failed to launch on biecuole:

Unable to establish ssh connection to [zhang@biecuole.local:22]: Server u'biecuole.local' not found in known_hosts

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