Added failure message when chart dependencies not satisfied

I keep having a problem when working on a new branch of running rspec and receiving a lot of failures because I don't pull in the chart dependencies. This usually takes me a minute or two to recognize what the real problem is. So here is a small bit of code to give a more meaningful error message to assist a user with fixing the environment to run the RSpec tests.

I have also seen an exit code of 2 on occasion, but I could not reproduce the error. So I have used a case statement so that other error conditions can be added easily.