[Bug 1752448] Re: error message for unmet dependencies is misleading

[Christophe Malek]

Feel free to word the new message in whatever way you feel is more
correct. The current message is definitely incorrect.

Your suggestion is fine with me:
libcupsimage2 : Depends: libcups2 (= 1.7.2-0ubuntu1.8) but 1.7.2-0ubuntu1.9 will remain installed.

Whether it is installed or not matters a lot to someone trying to
understand why they are getting an error message. As a package
management utility I'm sure apt should be able to detect what is
installed and give an appropriate message for either case.

If you think adding additional detection would overcomplicate the code then a more inclusive message could work too but is a little harder to read:
libcupsimage2 : Depends: libcups2 (= 1.7.2-0ubuntu1.8) but 1.7.2-0ubuntu1.9 is to be or will remain installed.

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Title:
  error message for unmet dependencies is misleading

Status in apt package in Ubuntu:
  New

Bug description:
  When trying to install some older packages on a machine with newer
  packages I get the following message:

  The following packages have unmet dependencies:
   libcupsimage2 : Depends: libcups2 (= 1.7.2-0ubuntu1.8) but 1.7.2-0ubuntu1.9 is to be installed
   libgfortran3 : Depends: gcc-4.8-base (= 4.8.4-2ubuntu1~14.04.3) but 4.8.4-2ubuntu1~14.04.4 is to be installed
  E: Unable to correct problems, you have held broken packages. 

  The way the message is worded makes it seem like I was trying to
  install version 1.7.2-0ubuntu1.9 and 4.8.4-2ubuntu1~14.04.4 of the
  above packages.

  In reality, these were the versions of the packages that were already
  installed on the machine.

  This caused a fair bit of confusion when trying to debug the
  situation.

  If you could please reword the error message to be correct. Perhaps
  something along the lines of:

  The following packages have unmet dependencies:
   libcupsimage2 : Depends: libcups2 (= 1.7.2-0ubuntu1.8) but 1.7.2-0ubuntu1.9 is already installed
   libgfortran3 : Depends: gcc-4.8-base (= 4.8.4-2ubuntu1~14.04.3) but 4.8.4-2ubuntu1~14.04.4 is already installed
  E: Unable to correct problems, you have held broken packages. 

  Thanks!

  ProblemType: Bug
  DistroRelease: Ubuntu 16.04
  Package: apt 1.2.25
  ProcVersionSignature: Ubuntu 4.13.0-36.40~16.04.1-generic 4.13.13
  Uname: Linux 4.13.0-36-generic x86_64
  ApportVersion: 2.20.1-0ubuntu2.15
  Architecture: amd64
  CurrentDesktop: Unity
  Date: Wed Feb 28 18:14:25 2018
  InstallationDate: Installed on 2017-11-03 (117 days ago)
  InstallationMedia: Ubuntu 16.04.3 LTS "Xenial Xerus" - Release amd64 (20170801)
  SourcePackage: apt
  UpgradeStatus: No upgrade log present (probably fresh install)

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