fix for issue 4047

[LeonardoSalvucci]

CLI will verify if args passed with --file exists and if not just ignore them and show a warning.

[jsf-clabot]

All committers have signed the CLA.

[outsideris]

#4047

[boneskull]

Thanks for the PR!

Like @outsideris wrote in the description of #4047, this should work like --require. So if you run mocha --require foo.js, and foo.js does not exist, an error will be printed and Mocha will exit. Instead, this prints a warning and continues. Can you please change the behavior?

I believe what you'll need to do is throw an exception instead of calling console.warn. Use throw createNoFilesMatchPatternError(msg) from lib/errors.js, where msg is Cannot find test file ${filename}