netplan 0.33 silently breaks bridge-priority

1.
# lsb_release -rd
Description: Ubuntu Bionic Beaver (development branch)
Release: 18.04
# cat /etc/cloud/build.info
build_name: server
serial: 20180224

2.
# apt-cache policy nplan
nplan:
  Installed: 0.33
  Candidate: 0.33
  Version table:
 *** 0.33 500
        500 http://archive.ubuntu.com/ubuntu bionic/main amd64 Packages
        100 /var/lib/dpkg/status

3. netplan configuration creates a bridge with a priority value and matches
the value in /sys/class/net/<bridge name>/bridge/priority

4. /sys/class/net/<bridge_name>/bridge/priority is the default value 32768 despite /etc/netplan/50-cloud-init.yaml specifies a priority value for the bridge.

--

The networkd renderer silently drops writing of Priority value to the [Bridge] section in a bridge's .netdev file.

The code says this:

netplan/src/networkd.c:69
#if 0
    /* FIXME: Priority= is not valid for the bridge itself, although it should work as the
         * STP priority of the bridge itself. It's not supported by networkd, but let's
         * keep it around in case it becomes supported in the future.
         */
        if (def->bridge_params.priority)
            g_string_append_printf(params, "Priority=%u\n", def->bridge_params.priority);
#endif

But bridge priority is settable via sysfs (with the bridge down) and via brctl setbridgeprio

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: nplan 0.33
ProcVersionSignature: Ubuntu 4.13.0-32.35~16.04.1-generic 4.13.13
Uname: Linux 4.13.0-32-generic x86_64
ApportVersion: 2.20.8-0ubuntu10
Architecture: amd64
Date: Tue Feb 27 20:14:24 2018
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 LANG=C.UTF-8
SourcePackage: nplan
UpgradeStatus: No upgrade log present (probably fresh install)