get return values instead of fatal errors

[mvogt1]

using eyaml in puppet like:

$method = lookup('secret::password_eyaml',String,undef,"INVALID")

is not fault tolerant. Everytime something goes wrong puppet aborts:

• if private key is not found -> fatal error
• if decoding fails -> fatal error

This is not how this should be handled. I like to get some status code so that I can react on the circumstances. The subsystem should not fail with error/exit.