invalid arg information not given, source of errors totally unclear

[benfleis]

Consider the trivial usage:

Usage:
  naval_fate.py new <name>

and a command line of: naval_fate.py new foo bar

The resulting output simply shows usage, with identifying the source of the problem.

Usage:
  naval_fate.py new <name>

It seems not only reasonable, but required that some context for the error be given.

After looking into the code, it is clear that it's available, but not bubbled up. PR coming shortly.