Remove use of pkg_resources from osrf_pycommon.

[clalancette]

Replace it with the use of the more modern importlib*
libraries. There are a couple of reasons to do this:

1. pkg_resources is quite slow to import; on my machine,
   just firing up the python interpreter takes ~35ms, while
   firing up the python interpreter and importing pkg_resources
   takes ~175ms. Firing up the python interpreter and importing
   importlib_metadata takes ~70ms. Removing 100ms per invocation
   of the command-line both makes it speedier for users, and
   will speed up our tests (which call out to the command-line
   quite a lot).

2. pkg_resources is somewhat deprecated and being replaced
   by importlib. https://importlib-metadata.readthedocs.io/en/latest/using.html
   describes some of it

Signed-off-by: Chris Lalancette clalancette@openrobotics.org

See ros2/ros2#919 for a lot more details on why we want to do this.

[wjwwood]

@clalancette I'm going to do one more release for Python2 before doing this.

addressed

[wjwwood]

Update on this, I've released versions 1.0.2 supporting < focal and 2.0.0 supporting >= focal. I released both to pip, and both to our bootstrap repository, making the python3-osrf-pycommon debs available for ROS 1 and 2's package repo.

I was going to release them into the current ROS 2 distributions, but after talking to @nuclearsandwich about it we may want to change that and the latest previous version (1.0.1) is not in foxy or galactic anyway. I added this to the next ROS 2 meeting's agenda.

[rgov]

I think this change introduced a regression on ROS 1 Noetic / Debian Buster, because there is no Python 3.8 package for that release, and hence the python3-osrf-pycommon package cannot be installed. See question on answers.ros.org.

Can version 1.0.2 please be re-released for Buster?

[wjwwood]

@rgov thanks for letting me know. I will look into this, sorry for the disruption. We did a split release which was supposed to avoid this (e.g. we have separate debs for Ubuntu <focal and >=focal), but maybe we messed it up for buster (Debian).

[nuclearsandwich]

I've opened #82 and #83 which update the release track for Debian Buster.

[wjwwood]

I'm doing the release today.

[wjwwood]

We've merged #82 and #83, released a 1.0.3 which includes buster, and pulled 2.0.0 for buster from our repos. I think that should be sufficient to fix your issue @rgov. I'm also going to release 2.0.1 which does not make a deb for buster, but that's just for consistency, it shouldn't be needed.

[wjwwood]

Thanks for reporting it!