Closes #13

* remove gdk-pixbuf-query-loaders workaround
* delete /var/cache/binpkgs/*
* rebuild dev-python/pycairo

fix #12

see https://wiki.gentoo.org/wiki/Binary_package_quickstart

This should solve:

  Package cairo was not found in the pkg-config search path.
  Perhaps you should add the directory containing `cairo.pc'
  to the PKG_CONFIG_PATH environment variable
  Package 'cairo', required by 'virtual:world', not found

see jvoisin/mat2!100

Unfortunately, the Gentoo build job fails regularly, and thus creates
noise reporting these errors. This change 'allows' such errors, which is
not a great solution, but at least leads to less emails.

Ref #10

This reverts commit 2f6f01fa.

This reverts commit 93d2a13e
See https://github.com/gentoo/gentoo-docker-images/issues/115#issuecomment-1020470812

https://bugs.gentoo.org/816303#c21
https://github.com/gentoo/gentoo-docker-images/issues/115

The following USE changes are necessary to proceed:
 (see "package.use" in the portage(5) man page for more details)
 required by x11-libs/pango-1.48.7::gentoo
 required by gnome-base/librsvg-2.50.7::gentoo
 required by gnome-base/librsvg (argument)
>=media-libs/freetype-2.10.4 harfbuzz

and fix circular dependencies

 * Error: circular dependencies:

(media-libs/harfbuzz-2.8.1:0/0.9.18::gentoo, ebuild scheduled for merge) depends on
 (media-libs/freetype-2.10.4:2/2::gentoo, ebuild scheduled for merge) (buildtime_slot_op)
  (media-libs/harfbuzz-2.8.1:0/0.9.18::gentoo, ebuild scheduled for merge) (buildtime)

 * Note that circular dependencies can often be avoided by temporarily
 * disabling USE flags that trigger optional dependencies.

see https://github.com/gentoo/gentoo-docker-images/pull/100
and https://github.com/gentoo/gentoo-docker-images/issues/97

DL3040 `dnf clean all` missing after dnf command.

DL3041 Specify version with `dnf install -y <package>-<version>`

Close: #9

This reverts commit dca08a0f.
Fixed in new images

!!! Multiple package instances within a single package slot have been pulled
!!! into the dependency graph, resulting in a slot conflict

Bug: https://github.com/gentoo/gentoo-docker-images/issues/79
Close: #7

According to the docs, this is frowned upon, as upgrading essential
packages might fail inside an unprivileged container.

That's a non-issue in our cases, as we're using privileged containers.

Further, we want to achieve the best of both worlds: we want to leverage
a build cache, to reduce build times, but, at the same time, we want to
pull in upgraded packages, in case the packages in question are already
installed.

This change should help with exposing errors like the one reported in
jvoisin/mat2#136 earlier in the future.

Relates jvoisin/mat2#136

Relates jvoisin/mat2#130

It seems, despite the name, both packages depend on Python 3. However,
pylint3 seems deprecated, and upstream recommends to install pylint:
https://www.pylint.org/#install

The current versions of both packages in Debian unstable are:
pylint  2.4.4-1
pylint3 2.2.2-1

This commit fixes failing CI jobs due to the use of pylint3 2.2.2-1,
which seems broken.

gentoo docker image is fixed upstream
see https://github.com/gentoo/gentoo-docker-images/issues/69