[Noetic] ign_ros_control stopped building on build farm

[sloretz]

Hey maintainers! I'm opening an issue here just as an FYI so you don't waste time investigating why ign_ros_control stopped building on the ROS Noetic buildfarm.

I suspect the root cause is a recent update to the gazebo packages in packages.ros.org ros-infrastructure/reprepro-updater#219 .

https://build.ros.org/view/Nbin_uF64/job/Nbin_uF64__ign_ros_control__ubuntu_focal_amd64__binary/23/console#:~:text=23%3A01%3A56%20Investigating%20(0)%20libignition%2Dgazebo3,Reinst%20Failed%20because%20of%20libignition%2Dgazebo3%3Aamd64

23:01:56 The following packages have unmet dependencies:
23:01:56  libignition-gazebo3-dev : Depends: libignition-gui3-dev (>= 3.11.0) but it is not going to be installed
23:01:56                            Depends: libignition-sensors3-dev (>= 3.3.0) but it is not going to be installed
23:01:56                            Depends: libignition-gazebo3 (= 3.15.1-1~focal) but it is not going to be installed
23:01:56                            Depends: libignition-gazebo3-plugins (= 3.15.1-1~focal) but it is not going to be installed
23:01:56 E: Unable to correct problems, you have held broken packages.

The problem is one of the dependencies of ign_ros_control, libignition-gazebo3-dev cannot be installed.

$ apt-get install libignition-gazebo3-dev
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 libignition-gazebo3-dev : Depends: libignition-gui3-dev (>= 3.11.0) but it is not going to be installed
                           Depends: libignition-sensors3-dev (>= 3.3.0) but it is not going to be installed
                           Depends: libignition-gazebo3 (= 3.15.1-1~focal) but it is not going to be installed
                           Depends: libignition-gazebo3-plugins (= 3.15.1-1~focal) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

Aptitude shows some packages have only older versions

The following packages have unmet dependencies:
 libignition-gazebo3 : Depends: libignition-rendering3 (>= 3.7.2) but 3.6.0-5~focal is to be installed
 libignition-sensors3-rgbd-camera : Depends: libignition-rendering3 (>= 3.7.2) but 3.6.0-5~focal is to be installed
 libignition-sensors3-camera : Depends: libignition-rendering3 (>= 3.7.2) but 3.6.0-5~focal is to be installed
 libignition-sensors3-thermal-camera : Depends: libignition-rendering3 (>= 3.7.2) but 3.6.0-5~focal is to be installed
 libignition-sensors3-rendering : Depends: libignition-rendering3 (>= 3.7.2) but 3.6.0-5~focal is to be installed
 libignition-gazebo3-plugins : Depends: libignition-rendering3 (>= 3.7.2) but 3.6.0-5~focal is to be installed
 libignition-sensors3-depth-camera : Depends: libignition-rendering3 (>= 3.7.2) but 3.6.0-5~focal is to be installed
 libignition-gui3 : Depends: libignition-rendering3 (>= 3.7.0) but 3.6.0-5~focal is to be installed

http://packages.ros.org/ros/ubuntu/dists/focal/main/binary-amd64/Packages shows at least libignition-rendering3 is still an older version

Package: libignition-rendering3
[...]
Version: 3.6.0-5~focal