Launchpad itself

E: Package build dependencies not satisfied; skipping

Asked by Neil Roza

This...

    https://launchpadlibrarian.net/469344807/buildlog_ubuntu-xenial-amd64.ros-kinetic-catkin_0.7.20-1xenialubuntu2_BUILDING.txt.gz

...wants the Build-Depends python-catkin-pkg. It fails to find python-catkin-pkg, but there it is, right there:

    https://launchpad.net/~realtime-robotics/+archive/ubuntu/test0001/+sourcepub/11063162/+listing-archive-extra

What am I doing wrong?

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Manfred Hampl (m-hampl) said : 		#1

The error message from your buildlog:
The following packages have unmet dependencies:
 sbuild-build-depends-ros-kinetic-catkin-dummy : Depends: python-catkin-pkg but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

The builder tries to install python-catkin-pkg but cannot, because python-catkin-pkg depends on python-catkin-pkg-modules which does not exist (or at least which I cannot find anywhere).

Control file of python-catkin-pkg:
Package: python-catkin-pkg
...
Depends: ... python-catkin-pkg-modules (>= 0.4.16)

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Neil Roza (realtime-neil) said : 		#2

Thanks very much for the explanation, Manfred. Where are you reading that bit about the missing python-catkin-pkg-modules? I can't find what you're quoting.

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Manfred Hampl (m-hampl) said : 		#3

In your buildlog for ros-kinetic-catkin you see

"Depends: python-catkin-pkg but it is not going to be installed"

This means that the package python-catkin-pkg is available, but cannot be installed for whatever reason - usually because of dependecies that cannot be fulfilled.

Now dig into the package python-catkin-pkg, especially into the control file. There you can see

"Package: python-catkin-pkg
...
Depends: ... python-catkin-pkg-modules (>= 0.4.16)"

I do not know a repository with the package python-catkin-pkg-modules (>= 0.4.16) for xenial, and the package builder also has not been told where to find it.

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Neil Roza (realtime-neil) said : 		#4

Oh, I know how to follow the `Depends` stanzas of control files --- I just didn't know if you found something in the buildlog that was as specific as your initial message. Pity that it didn't. Okay, thanks very much for your help.

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Manfred Hampl (m-hampl) said : 		#5

Just to confirm:
No, the root cause is not visible in the build log. You have to dig into the dependencies (or eventually also "breaks") of the dependent packages. It might even be the case that you have to go rather deep through the whole dependency chain to find the root cause.

In your case my first guess was successfull - but please note that I did not check whether there are other missing dependencies in addition to python-catkin-pkg-modules.