If container exits on error, eventually important information from stdout is omitted

[bionade24]

Example ros-melodic-moveit-perception: https://abs-cd.oscloud.info/cd_manager/ros-melodic-moveit-ros-perception
Real part of stdout + stderr combined:

Total Installed Size:  1423.30 MiB                                                                                                                                                                        
                                                                                                                                                                                                          
:: Proceed with installation? [Y/n]                                                                                                                                                                       
checking keyring...                                                                                                                                                                                       
checking package integrity...                                                                                                                                                                             
loading package files...                                                                                                                                                                                  
checking for file conflicts...                                                                                                                                                                            
error: failed to commit transaction (conflicting files)                                                                                                                                                   
/opt/ros/melodic/lib/python3.9/site-packages/libgtest.so exists in both 'ros-melodic-moveit-core' and 'ros-melodic-tf'                                                                                    
/opt/ros/melodic/lib/python3.9/site-packages/libgtest.so.1.10.0 exists in both 'ros-melodic-moveit-core' and 'ros-melodic-tf'                                                                             
Errors occurred, no packages were upgraded.                                                                                                                                                               
==> ERROR: 'pacman' failed to install missing dependencies.                                                                                                                                               
==> Missing dependencies:                                                                                                                                                                                 
  -> ros-build-tools                                                                                                                                                                                      
  -> ros-melodic-message-filters                                                                                                                                                                          
  -> ros-melodic-moveit-core                                                                                                                                                                              
  -> ros-melodic-moveit-msgs           

Shown in abs_cd:

warning: dependency cycle detected:
warning: harfbuzz will be installed before its freetype2 dependency
warning: dependency cycle detected:
warning: libglvnd will be installed before its mesa dependency
error: failed to commit transaction (conflicting files)
==> ERROR: 'pacman' failed to install missing dependencies.
warning: dependency cycle detected:
warning: harfbuzz will be installed before its freetype2 dependency
warning: dependency cycle detected:
warning: libglvnd will be installed before its mesa dependency
error: failed to commit transaction (conflicting files)
==> ERROR: 'pacman' failed to install missing dependencies.
==> ERROR: Could not resolve all dependencies.
No packages were built!

@fmauch Tagging you as it affects you.

Proposed solutions:

1. Pacman should imho put all important error information to stderr -> Upstream bug
2. Capture both logs on error cases, too. The docker API for Python makes this unnecessary complicated imao. ContainerError only has stderr as member. The current implementation can't work that way, we would have need to run containers with detach=True and remove=False to get the container logs after exited on failiure IIRC. -> I'll try to propose adding an output member upstream.

We still could fix this temporarily if necessary.

[fmauch]

Thanks for summing this up. I remember having a short discussion about this in an email with you a while ago, but that's a prime example showing the actual problem.

[bionade24]

Thanks for summing this up. I remember having a short discussion about this in an email with you a while ago, but that's a prime example showing the actual problem.

Yeah, back then I didn't take your argument, but you were right. In this case the actual error message is omitted.

[bionade24]

Seems like it's easy to solve and I was wrong about the upstream problem. docker/docker-py#2745

[bionade24]

Fixed f046d5b