prerm is in elpa-company 0.9.4-1.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 | #!/bin/sh
set -e
# Pre-emptively upgrade emacsen-common remove script to deal with several
# possible issues when upgrading from version 0.8.12-4 or older.  These can
# cause the emacsen-common remove script to exit non-zero, breaking the package
# upgrade
if [ "$1" = "failed-upgrade" ] && dpkg --compare-versions "$2" lt 0.8.12-5; then
    broken_remove_script="/usr/lib/emacsen-common/packages/remove/elpa-company"
    # (1) exit cleanly for xemacs21 -- without this, the call to find(1) can
    # exit non-zero
    sed --quiet -i "$broken_remove_script" \
        -e '/Skipping unsupported emacs ${FLAVOUR}/a \           exit 0'
    # (2) exit cleanly for yet older unsupported Emacsen that might be installed
    sed --quiet -i "$broken_remove_script" \
        -e 's/emacs23)/emacs2[0123]*)/'
fi
# Automatically added by dh_elpa/UNDECLARED
if [ -e /var/lib/emacsen-common/state/package/installed/emacsen-common -a -x /usr/lib/emacsen-common/emacs-package-remove ] ; then
	/usr/lib/emacsen-common/emacs-package-remove --prerm elpa-company
fi
# End automatically added section
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