or an error has the class "error" and appears in red font.

https://github.com/swcarpentry/lesson-example/blob/gh-pages/LAYOUT.md#topics

This avoids things like:

  ~$ cat tools/validation_helpers.py
  ...
          return self.is_block(ast_node) and has_heading~$

with your next prompt way over to the right ;).

default instead of figure/.

1.  Adding `tools/chunk-options.R` with support for Pandoc-based conversion of R Markdown to plain Markdown.
2.  Modifying `Makefile` to handle any R Markdown files that are present.

Changes have been checked by @jdblischak in the `r-novice-inflammation` project.