title: robotframework/rfdocker says it is python3 and debian buster based but cannot use apt-get in Dockerfile
body: <p>As the title says when I try to run an 'apt-get -y update' command when building my Robotframework Dockerfile I get the error below:</p>
  <p><em>/bin/sh: apt-get: not found</em></p>
  <p><em>executor failed running [/bin/sh -c apt-get -y update]: exit code: 127</em></p>
  <p>Can anyone help in explaining why this is the case as per my understanding this should run due to the Debian Buster base?</p>