Updating Ubuntu package libunity-scopes1.0 1.0.2+15.10.20150921-0ubuntu1 failed to install/upgrade: subprocess installed pre-removal script returned error exit status 1

This doesn't look like a scopes-api problem. DpkgTerminalLog.txt seems to indicate click.

Status changed to 'Confirmed' because the bug affects multiple users.

click has the right dependencies here (click Depends: python3-click Depends: python3-apt Depends: libapt-pkg4.16). The problem is that unity-scope-click.prerm (the relevant bit of which is in fact generated by dh_click, so this isn't passing the buck) is calling click in a situation where click may be technically in an unconfigured state: in particular this is probably mid-way through upgrading the packages that form part of the g++ 5 transition between 15.04 and 15.10, so libapt-pkg and python-apt are temporarily in a rather sad state.

I don't think that strengthening dependencies is the answer here; instead, we need to make things more robust against being run in this kind of situation. The good news is that apt_pkg is only used in a few places in click, and they almost all tolerate it not being importable. The one exception is click.install, which originally imported apt_pkg because it used it to parse framework entries in manifests. That has since moved to click.framework, though, and the code there now copes with this situation.

It therefore looks as though we can just drop the apt_pkg bits from click.install and all will be well.

This bug was fixed in the package click - 0.4.41+16.04.20151211-0ubuntu1

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click (0.4.41+16.04.20151211-0ubuntu1) xenial; urgency=medium

  [ Colin Watson ]
  * Fix spurious test_sync_without_user_db test failure.
  * Fix test failures under Python 2.
  * Forbid installing packages with data tarball members whose names do not
    start with "./" (LP: #1506467).
  * Take evasive action in case the conflicting "click" package has been
    installed locally from PyPI (LP: #1486841).
  * Drop use of apt_pkg from click.install, since it's no longer needed
    there (LP: #1510015).

  [ Dimitri John Ledkov ]
  * Require specific Click version, to avoid gi warnings that fail
    test-suite (LP: #1522608).
  * Set Vcs-* fields to the actual development branch.

  [ CI Train Bot ]
  * No-change rebuild.

 -- Colin Watson <email address hidden> Fri, 11 Dec 2015 01:31:29 +0000