Suggest `brew update && …` when handling errors or missing methods

As @ndr-qef and @rolandwalker suggested on IRC.

This is supposed to help cut trivial issues that would be easily fixable by doing `brew update && …` etc.
Also, splitting unit tests in two to keep one from triggering the other.

Then it is a clever trick.

You are free to do as you please, in heredocs and elsewhere.  We can adopt a style re: wrapping across the codebase if it benefits you.  I tend to let code run wide, which attracts criticism.