openstack horizion material themes invalid icon content generated via pyScss 1.3.5

[cygmris]

Under Ubuntu:Bionic with latest packages installed (including apt installed version of pyScss 1.3.5), The icons are being compiled wrong with content 'xf101' instead of '\f101'.

After downgrade pyScss to 1.3.4, icon content displayed normally.

Check:

• https://bugs.launchpad.net/horizon/+bug/1771559
• https://github.com/openstack/horizon/blob/master/openstack_dashboard/themes/material/static/horizon/_icons.scss

and static/horizon/lib/mdi/scss/_icons.scss

@function char($character-code) {
    @if function-exists("selector-append") {
        @return unquote("\"\\#{$character-code}\"");
    }
    @if "\\#{'x'}" == "\\x" {
        @return str-slice("\x", 1, 1) + $character-code;
    } @else {
        @return #{"\"\\"}#{$character-code + "\""};
    }
}

@function mdi($name) {
    @return char(nth($hexes, index($names, $name)));
}

@for $i from 1 through length($hexes) {
    .#{$mdi-css-prefix}-#{nth($names, $i)}:before {
        content: char(nth($hexes, $i));
    }
}

hexes is string like 'f101 '.