This is to debug https://groups.google.com/d/msg/sage-devel/WshDn3e_l3k/-smgNej4AwAJ

https://hub.docker.com/r/vbatts/slackware/tags

This enables the following tests:

   tox -e docker-slackware-14.2-minimal
   tox -e docker-slackware-14.2-standard

Random slackware links:

• https://software.jaos.org/#slapt-get

CC: @jhpalmieri @dimpase @videlec

Component: porting

Author: Matthias Koeppe

Branch: c1931f5

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/29354