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Unmet dependencies: python-catkin-pkg : Conflicts: catkin but 0.7.8-1 is to be installed

I followed the instructions to install ros-melodic-desktop-full on Ubuntu 18.04 from http://wiki.ros.org/melodic/Installation/Ubuntu. I noticed the command rosbag was not installed which requires installing python-rosbag.

When I try sudo apt install python-rosbag, I get the following error: 

The following packages have unmet dependencies:
 python-catkin-pkg-modules : Conflicts: catkin but 0.7.8-1 is to be installed
 python-catkin-pkg : Conflicts: catkin but 0.7.8-1 is to be installed

Running sudo aptitude install python-rosbag doesn't resolve the issue. No hints either on http://wiki.ros.org/UpstreamPackages. I made sure all repositories are turned on, and 'source /opt/ros/melodic/setup.bash' is at the of my .bashrc.

Does anyone else have any other suggestions?

Thanks in advance

Asked by michago on 2018-10-26 06:16:24 UTC

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Did you also install the catkin package separately? ros-melodic-desktop-full depends on ros-melodic-catkin which depends on python-catkin-pkg and python-catkin-pkg-modules. The last two conflict with catkin. You mention you used aptitude, but it "didn't solve the issue"...

Asked by jarvisschultz on 2018-10-26 07:35:59 UTC

I would think that aptitude would be capable of resolving this if you really parsed the options it provides. Regardless, the issue seems to be that you likely installed some packages manually that you shouldn't have and now dependencies can't be automatically installed because they conflict.

Asked by jarvisschultz on 2018-10-26 07:37:59 UTC

Note that apt-cache depends <PKGNAME> can tell you dependencies. The --recurse option will produce recursive dependencies. Also I usually use dpkg -l | grep <PKGNAME> to search for packages that I do have installed. In that output anything with an ii at the beginning of the line is installed

Asked by jarvisschultz on 2018-10-26 07:40:07 UTC

@jarvisschultz: the issue is not with Catkin, but with the python-rosbag upstream package trying to bring in conflicting dependencies.

Asked by gvdhoorn on 2018-10-26 07:41:19 UTC

Yeah you must be right, and I should have gotten that from him explicitly mentioning he installed that manually.

Asked by jarvisschultz on 2018-10-26 11:29:12 UTC

Answers

I noticed the command rosbag was not installed which requires installing python-rosbag.

Actually: no.

The correct package name is ros-$ROS_DISTRO-rosbag.

python-rosbag is the "upstream" version, as explained on the Debian Science pages linked from the wiki/UpstreamPackages you already link.

Asked by gvdhoorn on 2018-10-26 07:31:55 UTC

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After uninstalling and installing ROS trying to deal with the issue, now I notice that the command rosbag is present. You're right, ros-melodic-rosbag package must not have been previously installed for some reason. Though python-rosbag won't install, there's no reason to do it as the command I need is present. Thanks a lot to all for your quick responses.

Asked by michago on 2018-10-26 07:52:08 UTC

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