As I expected, on Google App Engine we can't write the cache file
to the current working directory. I modified csv-metadata-quality
CLI to check for the REQUESTS_CACHE_DIR environment variable so we
don't really have to do anything different other than setting the
variable.
Refactor the templates to include a header, use csv-metadata-quality
in a subshell instead of trying to import and pass args to it (which
I actually managed to do, but then trying to capture the output was
an issue), and use ansi2html to prepare the CLI output as the HTML.