class Drydock::ArgError

def initialize(*args)
  @msg = args.shift if args.size == 1
  @arg, @cmd, @msg = *args
  @cmd ||= 'COMMAND'
  @msg = nil if @msg && @msg.empty?
  super
end

def message
  @msg || "Error: No #{@arg} provided"
end

def usage
  "See: #{$0} #{@cmd} -h"
end