When attempting to do llama-perplexity on certain tasks which have coupled sequences there is a cryptic error that does not tell you what to do, which is to set the -kvu flag. This adds a hint about that fact.
* perplexity: give more information about constraints on failure
This checks whether -np is insufficient vs context, and provides clues as to how much is needed for each.
* log formatting
* log error and return instead of storing max_seq_exceeded int
* check if s0 is zero for -np check