Print human error message for pid file failures
Print human error message for pid file failures

This prints a much more pretty error message if nipapd fails to open the
pid file.

Fixes #137

plajjan/NIPAP,bbaja42/NIPAP,ettrig/NIPAP,garberg/NIPAP,SpriteLink/NIPAP,SoundGoof/NIPAP,fredsod/NIPAP,ettrig/NIPAP,bbaja42/NIPAP,SoundGoof/NIPAP,garberg/NIPAP,plajjan/NIPAP,bbaja42/NIPAP,SoundGoof/NIPAP,SpriteLink/NIPAP,SoundGoof/NIPAP,fredsod/NIPAP,SpriteLink/NIPAP,garberg/NIPAP,ettrig/NIPAP,bbaja42/NIPAP,ettrig/NIPAP,SpriteLink/NIPAP,plajjan/NIPAP,ettrig/NIPAP,bbaja42/NIPAP,fredsod/NIPAP,garberg/NIPAP,plajjan/NIPAP,plajjan/NIPAP,garberg/NIPAP,fredsod/NIPAP,garberg/NIPAP,bbaja42/NIPAP,SoundGoof/NIPAP,SoundGoof/NIPAP,ettrig/NIPAP,fredsod/NIPAP,fredsod/NIPAP,plajjan/NIPAP,SpriteLink/NIPAP,SpriteLink/NIPAP