Better error messages when parameters passed to arrow result in invalid configuration

[rothshahar]

I'd like arrow to provide better error messages when an error occur. It wasn't vocal enough and it was hard to understand the cause for the failure.

For example, I wrote a yui test but accidentally passed --engine mocha. Arrow timed out after a minute and showed the following text from the console:

[LOG] [LOG]

It took me a long time to understand the mistake. Arrow should be more vocal when users pass command line parameters that result in bad configuration.

I think a similar problem occurs if you pass an invalid path to --engineConfig for example.

[proverma]

Thanks for reporting this, makes total sense. We will add these error checks to v0.6 release.