You can read this ticket for a summary of the issues and workarounds:

https://code.ros.org/trac/ros/ticket/3136

The gist is that, while Debian systems support "python2" vs. "python3"
as an explicit executable, OS X does not. In my opinion, arch made a
bad choice. Even docs.python.org uses Python 2.x as the default
documentation set. For Python users, it makes more sense to migrate to
"python3" than to back-migrate everything to "python2".

 - Ken

On Sun, Nov 14, 2010 at 12:57 AM, Soo-Hyun Yoo <yoos117@gmail.com> wrote:
> I received the same errors today: http://pastebin.com/b70kSndj
> This is due to the recent change that points /usr/bin/python to python-3.x.
> The only workaround I could think of was to remove the symlink and point it
> instead to /usr/bin/python2.7, after which ROS successfully installed and
> compiled.
> Does anyone know if there is an "official" fix?
> Soo-Hyun Yoo
>
> On Fri, Oct 22, 2010 at 5:00 PM, Morgan Quigley <mquigley@cs.stanford.edu>
> wrote:
>>
>> I haven't used Arch in a while now, since I finally converted to
>> Ubuntu last year. I'm not sure if there is anybody else using ROS
>> actively on Arch, but if so they will hopefully chime in.
>>
>> To get that error, did you download the rosinstall script and just run
>> it, or did you try to build rospack manually?
>>
>> -Morgan
>>
>>
>> On Fri, Oct 22, 2010 at 2:49 AM, Tadele Shiferaw <metitad@gmail.com>
>> wrote:
>> >  I am trying to install ROS on archlinux and I get the following error
>> > when trying to use rosinstall...
>> >
>> > print "Rospack failed to build"
>> >                                  ^
>> > SyntaxError: invalid syntax
>> > Traceback (most recent call last):
>> >  File "/usr/bin/rosinstall", line 5, in <module>
>> >    pkg_resources.run_script('rosinstall==0.5.8', 'rosinstall')
>> >  File "/usr/lib/python2.7/site-packages/pkg_resources.py", line 489, in
>> > run_script
>> >    self.require(requires)[0].run_script(script_name, ns)
>> >  File "/usr/lib/python2.7/site-packages/pkg_resources.py", line 1214, in
>> > run_script
>> >    exec script_code in namespace, namespace
>> >  File
>> > "/usr/lib/python2.7/site-packages/rosinstall-0.5.8-py2.7.egg/EGG-INFO/scripts/rosinstall",
>> > line 501, in <module>
>> >
>> >  File
>> > "/usr/lib/python2.7/site-packages/rosinstall-0.5.8-py2.7.egg/EGG-INFO/scripts/rosinstall",
>> > line 492, in rosinstall_main
>> >
>> >  File "/usr/lib/python2.7/subprocess.py", line 504, in check_call
>> >    raise CalledProcessError(retcode, cmd)
>> > subprocess.CalledProcessError: Command 'source /home/user1/ros/setup.sh
>> > && rosmake rostest --rosdep-install' returned non-zero exit status 1
>> >
>> >
>> > Any help is appreciated
>> > _______________________________________________
>> > ros-users mailing list
>> > ros-users@code.ros.org
>> > https://code.ros.org/mailman/listinfo/ros-users
>> >
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