post_upgrade() {
    if (( $(vercmp 0.9.13 "$2") > 0 )); then
        cat << __EOF__
Sigil will very possibly not work at first due to bugs in the 0.9.11 - 0.9.12 preferences code.
Please see the following resources for migration instructions:
  https://www.mobileread.com/forums/showthread.php?t=315748
  https://github.com/Sigil-Ebook/Sigil/wiki#if-youre-here-because
__EOF__
    fi
}