add missing python3 dep

[artivis]

Closes #23 .

[artivis]

Hi @cottsay, any chance to get a quick look at this?

[cottsay]

I put this on the infrastructure agenda to discuss on Monday, and I'll ping back here with any findings.

I informally proposed the same change a few years back after stumbling across the same issue. Though I'm not involved or up-to-date on the effort, there is a desire for "python-free ROS 2" and even though some of the stuff in this package requires Python, this package can still be used without it.

In the RPMs, I made Python a soft dependency: https://github.com/ros2-gbp/ros_workspace-release/blob/patches/rpm/rolling/ros_workspace/0001-Bootstrap-PYTHONPATH-and-inject-Python-3-dependency.patch

Maybe we can do something similar for the debs.

[artivis]

this package can still be used without it

Well I guess that depends on one's definition of usable. If I can't source the ROS workspace this packages is meant to set up what is it good for?

Note that there are entire dependency trees (certainly very few) that do not include python3 such as e.g. that of kdl_parser,

$ apt-cache depends --recurse --no-recommends --no-suggests --no-conflicts --no-breaks --no-replaces --no-enhances ros-foxy-kdl-parser | grep "^\w" | sort -u
dpkg
gcc-10-base
libacl1
libblkid1
libbz2-1.0
libc6
libconsole-bridge0.4
libconsole-bridge-dev
libcrypt1
libdb5.3
libdpkg-perl
libeigen3-dev
libffi7
libgcc-s1
libgdbm6
libgdbm-compat4
libglib2.0-0
liblzma5
libmount1
libpcre2-8-0
libpcre3
libperl5.30
libpkgconf3
libselinux1
libstdc++6
libtinyxml2.6.2v5
libtinyxml-dev
libzstd1
perl
perl-base
perl-modules-5.30
pkgconf
pkg-config
ros-foxy-console-bridge-vendor
ros-foxy-eigen3-cmake-module
ros-foxy-kdl-parser
ros-foxy-orocos-kdl
ros-foxy-ros-workspace
ros-foxy-tinyxml-vendor
ros-foxy-urdf
ros-foxy-urdfdom
ros-foxy-urdfdom-headers
tar
zlib1g

Looking forward to next week ping back,
Thanks!

[artivis]

Hi @cottsay, any updates on this?

[cottsay]

We had the periodic Infrastructure Team Office Hours in place of our weekly meeting this week. It will have to wait until next week.

[artivis]

Hello, friendly ping :)

[nuclearsandwich]

@cottsay brought this up in today's meeting. In the past there was strong resistance to this because it introduces python at the lowest levels of the ROS package hierarchy, stymieing efforts to create a ROS 2 without Python installation.

It's unclear if any such efforts are still underway or using the apt packages for ROS 2 at all. I think that the user experience improvement of having python is strong enough to make it a required dependency.

If there is a need in the future we can always discuss patching the bloom package to put it into recommended/suggested (I forget which is the greater strength).