apt-key broken, exit code 2

I was trying to add a PGP key for non-Ubuntu packages when I realized that any apt-key request is doing nothing (no output, no configuration change) and the program exit with code 2, except for --usage.

How can I fix it? Is there a debug output file of apt-key? Or in last case, is there a way to reinstall easily apt/apt-key without destroying my current configuration?