Comment 1 for bug 1864033

Curtinator doesn't know about 18.04, this results in this rather obtuse error.

There's a table of known Ubuntu versions around line 169:

function patch_initrd() {
    local distribution=$1; shift
    local initrd=$1; shift
    local files=$@

    local bs=""

    temp=$(mktemp)

    # only needed for 18.10 and beyond
    # the following are also released later than 18.10
    # 14.04.6
    # 18.04.3
    case $distribution in
        14.04.6) bs=1576592;;
        16.04.6) bs=1605632;;
        18.04.3) bs=2441216;;
        18.10) bs=1605632;;
        19.04) bs=2092032;;
    esac

This needs to be augmented with 18.04, but I don't know how to obtain the correct bs value. I think taihsiang would need to determine that.