Define xrange() for Python 3

[cclauss]

xrange() is called 21 times in this file but it was removed from Python 3 in favor of range().

[mikepurvis]

Interesting situation. It seems the upstream version of this still has the problem you describe, so just bumping that doesn't do any good:

https://github.com/google/styleguide/blob/gh-pages/cpplint/cpplint.py

In the past my preference has been to monkey-patch cpplint so it's easier to periodically pull the new upstream version, but this isn't really a monkey-patchable change.

[cclauss]

Thanks Mike... I will try to push this change into upstream.

What is ROS' general position on migrating to Python 3? I could help out there but want to do so in ways that do not rub maintainers the wrong way. Reading thru upstream as you suggested, I came across https://github.com/google/styleguide/blob/cfce3c3a866cfa9ec12fff08d5e575ca875f787b/pyguide.md#the-six-future-or-past-libraries Does ROS have a POV on the use of six to achieve compatibility with both Python 2 and Python 3?

[mikepurvis]

Everything in ros_base (which includes this repo) is theoretically bilingual. However, Python 3 is not the default Python on any current Ubuntu LTS, so OSRF hasn't got ongoing test coverage for Python 3, meaning there are frequent regressions.

In terms of larger policy around a migration plan, feel free to join the fray: ros-infrastructure/rep#149