Bug#933859: apt-cudf doesn't work with "apt install ./*.deb"

[Simon McVittie <smcv@debian.org>]

Package: apt,apt-cudf
Version: 1.8.2,5.0.1-12+b1
Severity: normal

I tried to solve <https://salsa.debian.org/salsa-ci-team/pipeline/issues/58>
by configuring piuparts to be willing to take the versioned dependencies
of the package under test from experimental, by configuring apt in the
piuparts chroot to use apt-cudf and aspcud, but I was not successful.

Steps to reproduce outside piuparts (I used a sid VM):

* Have sid and experimental apt sources
* sudo apt install apt-cudf aspcud
* Have a .deb whose dependencies cannot be satisfied in sid, for example
  gnome-shell 3.32.2-2 as of today:
  apt-get -t experimental download gnome-shell
* Configure aspcud resolver with the same setup as official Debian
  experimental buildds:
  (<https://salsa.debian.org/dsa-team/mirror/dsa-puppet/blob/master/modules/buildd/files/sbuild.conf>)

sudo tee /etc/apt/apt.conf.d/aspcud <<EOF
APT::Solver "aspcud";
APT::Solver::Strict-Pinning "no";
APT::Solver::aspcud::Preferences "-removed,-changed,-new,-count(solution,APT-Release:=/experimental/)";
EOF

* sudo apt install ./gnome-shell_3.32.2-2_amd64.deb

Expected result:

apt-cudf selects gnome-shell's dependency libmutter-4-0 (and probably
others) from experimental

Actual result:

> Fatal error: exception Common.Format822.ParseError(_, "Provides", "Field Provides has a wrong value (character 0-1: character 0-1: Unexpected token : '.'.. (vpkglist)): './gnome-shell_3.32.2-2_amd64.deb (= 3.32.2-2), polkit-1-auth-agent, notification-daemon'")

I'm not sure whether this is an apt bug (giving wrong data to apt-cudf)
or an apt-cudf bug (not accepting valid data from apt). Any ideas?

Thanks,
    smcv