# File lib/cliver.rb, line 59
  def self.verify!(executable, *args, &block)
    unless File.absolute_path?(executable)
      raise ArgumentError, "executable path must be absolute, " +
                           "got '#{executable.inspect}'."
    end
    options = args.last.kind_of?(Hash) ? args.pop : {}
    args << options.merge(:path => '.') # ensure path non-empty.
    Dependency::new(executable, *args, &block).detect!
  end