[Review] Request from 'greygoo' @ 'SUSE/machinery/review_140731_dont_cut_error_messages'

Please review the following changes:
  * 32a5f11 Changed Cheetah exceptions to show all standard error output.
Maybe better specific:

```ruby
begin
  # Actually raise the exception, so we have a backtrace
  raise(Cheetah::ExecutionFailed.new(nil, nil, "This is STDOUT", "This is STDERR"))
rescue => e
  expect(Cli.handle_error(e)).to to raise_error(SystemExit)
end
```