Comment 5 for bug 458163

A bit more explanation...

Before euca_rootwrap was rewritten:
 * powerwake ran as root:root
 * thus, powerwake had write access to /var/cache/powerwake/ethers
 * and powerwake worked just fine

After euca_rootwrap was rewritten:
 * powerwake was whitelisted, but wasn't given root access
 * now, powerwake runs as eucalyptus:eucalyptus
 * which is fine to send the magic WoL packet
 * however, the cache file is not writable
 * and thus, powerwake now itself throws an exception

As stated above, we can fix this entirely in powerwake with a trivial fix, testing W_OK on /var/cache/powerwake/ethers.

:-Dustin