Add an element to purge c-n-f packages

Author: m-bull

elements/purge-command-not-found/README.rst

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+========================
+purge-command-not-found
+========================
+Purge command-not-found packages from an image.
+
+Currently the pulp_deb plugin in Pulp does not support certain types of
+content, including i18n files and command-not-found indices. This breaks APT
+when the command-not-found is installed. This element can be used to
+uninstall the package, prior to running any other APT commands that may target
+Pulp package mirrors.
+
+No additional configuration is needed, other than including the element.

elements/purge-command-not-found/pre-install.d/02-purge-command-not-found

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+#!/bin/bash
+if [ ${DIB_DEBUG_TRACE:-0} -gt 0 ]; then
+    set -x
+fi
+set -eu
+set -o pipefail
+
+sudo apt purge -y command-not-found