Summary and Info:

When desc files are missing in /var/lib/pacman/local/*/ pacman print error on stdout in place of stderr.

archipel ~ 1 # pacman -Qs toto 2>/dev/null
error: could not open file /var/lib/pacman/local/xterm-270-1/desc: No such file or directory
...

This impact some capacities of pacman. By example when was filesystem is corrupted and you want to reinstall all your system, doing something like wiki suggest it is impossible:

pacman -S $(comm -23 <(pacman -Qeq) <(pacman -Qmq))

Another impact is when you call makepkg, you can see output in attachment.

I looked into the code and i don't find an easy way to fix. I will look more closely later.

Steps to Reproduce:
Remove a file like /var/lib/pacman/local/xterm*/desc