Installing ROS Indigo on NAO: problem with yaml

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Hello

I'm trying to install ROS Indigo on a NAO V4 with OpenNao 1.14.5.

Following the tutorial "Installation of ROS on the Nao robot " ( http://wiki.ros.org/nao/Installation/... ) I had an issue starting ROS on NAO:

roslaunch nao_bringup nao.launch gives me the following output:

Traceback (most recent call last):
  File "/opt/openrobots/bin/roslaunch", line 34, in <module>
    import roslaunch
  File "/var/persistent/opt/openrobots/lib/python2.7/site-packages/roslaunch/__init__.py", line 51, in <module>
    from . import param_dump as roslaunch_param_dump
  File "/var/persistent/opt/openrobots/lib/python2.7/site-packages/roslaunch/param_dump.py", line 40, in <module>
    import roslaunch.config
  File "/var/persistent/opt/openrobots/lib/python2.7/site-packages/roslaunch/config.py", line 45, in <module>
    import rospkg.distro
  File "/var/persistent/opt/openrobots/lib/python2.7/site-packages/rospkg/distro.py", line 44, in <module>
    import yaml
ImportError: No module named yaml

I tried to re-install yaml (sudo emerge pyyaml) and got this error as a result:

ERROR: app-admin/eselect-python-20100321 failed (setup phase):
 *   GCC >=3.4 is required
 * 
 * Call stack:
 *     ebuild.sh, line  75:  Called pkg_setup
 *   environment, line 636:  Called die
 * The specific snippet of code:
 *           die "GCC >=3.4 is required";

Therefore has anyone an idea of how to correctly install pyyaml on NAO?

Thank You very much :)