Altering error message to show the exception

[catharsisjelly]

See #6390

[helpfulrobot]

@catharsisjelly, thanks for your PR! By analyzing the blame information on this pull request, I identified @assertchris, @chillu and @wilr to be potential reviewers

[tractorcow]

It's too risky to be displaying error messages contained in exceptions outside of dev mode, as these could contain potentially sensitive information.

You can get around this with a conditional Director::isDev() ? print('explicit message') : print('simple message')

[catharsisjelly]

@tractorcow Made a change based on your suggestion to this PR

[tractorcow]

Nice job. :D