ROS install Yaml error on OSX

edit

Ive been trying to install ROS and have been given this error at the end of running:

rosinstall ~/ros "http://packages.ros.org/cgi-bin/gen_rosinstall.py?rosdistro=diamondback&variant=desktop-full&overlay=no"

ERROR:

import yaml
ImportError: No module named yaml
Traceback (most recent call last):
  File "/usr/local/bin/rosinstall", line 5, in <module>
    pkg_resources.run_script('rosinstall==0.5.16', 'rosinstall')
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/pkg_resources.py", line 442, in run_script
    self.require(requires)[0].run_script(script_name, ns)
  File "/System/Library/Frameworks/Python.framework/Versions/2.6/Extras/lib/python/pkg_resources.py", line 1167, in run_script
    exec script_code in namespace, namespace
  File "/Library/Python/2.6/site-packages/rosinstall-0.5.16-py2.6.egg/EGG-INFO/scripts/rosinstall", line 556, in <module>

  File "/Library/Python/2.6/site-packages/rosinstall-0.5.16-py2.6.egg/EGG-INFO/scripts/rosinstall", line 547, in rosinstall_main

  File "/System/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/subprocess.py", line 462, in check_call
    raise CalledProcessError(retcode, cmd)
subprocess.CalledProcessError: Command 'source /Users/ic/ros/setup.sh && rosmake ros ros_comm --rosdep-install' returned non-zero exit status 1

I already run the sudo easy_install -U pyyaml command and that seemed fine but i still end up with this error any ideas?

Thanks