Note that this patch does 2 things:

1. Improves the error message
2. Prevents check from failing when there are code-blocks

If I only did #1 and not #2, then output looks like this:

$ python setup.py check --restructuredtext --strict --metadata && echo "RST was OK."
running check
warning: check: Could not finish the parsing: 'Values' object has no attribute 'syntax_highlight'.

error: Please correct your package.