While the workaround for this bug is fairly straightforward (apt-get install php-fpm), this doesn't negate the fact that this bug makes "apt-get install mysqladmin" cause lighttpd to fail and refuse to start up. It also caused the initial install to fail and left the package in a partially installed state.
When installing one package causes another, a major subsystem at that, to fail, I would recommend the severity be at least "serious".
