colorize html output when batch exporting

[Alan Schmitt <alan.schmitt@polytechnique.org>]

Hello,

I'm trying to batch export a file, and I don't seem to have colorization
working. Reading the documentation a bit, I found this information:

,----
| org-html-htmlize-output-type is a variable defined in `ox-html.el'.
| Its value is inline-css
| 
| Documentation:
| Output type to be used by htmlize when formatting code snippets.
| Choices are `css', to export the CSS selectors only, or `inline-css', to
| export the CSS attribute values inline in the HTML.  We use as default
| `inline-css', in order to make the resulting HTML self-containing.
| 
| However, this will fail when using Emacs in batch mode for export, because
| then no rich font definitions are in place.  It will also not be good if
| people with different Emacs setup contribute HTML files to a website,
| because the fonts will represent the individual setups.  In these cases,
| it is much better to let Org/Htmlize assign classes only, and to use
| a style file to define the look of these classes.
| To get a start for your css file, start Emacs session and make sure that
| all the faces you are interested in are defined, for example by loading files
| in all modes you want.  Then, use the command
| M-x org-html-htmlize-generate-css to extract class definitions.
`----

Following these instructions, I set up this variable in the init.el
called upon batch exporting, among other things:

#+BEGIN_SRC emacs-lisp
(add-to-list 'load-path (file-name-directory load-file-name))

(require 'local_settings)

(require 'org)
(require 'ox-html)

(setq org-html-postamble nil)
(setq org-html-htmlize-output-type 'css)
(setq org-confirm-babel-evaluate nil)
#+END_SRC

Unfortunately I could not complete the next step (to get a start on the
css file), as `org-html-htmlize-generate-css` results in an error
"face-attribute: Invalid face: font-lock-comment". I tried to toggle
debug on error, but it does nothing.

Are there suggestions on how to generate this css file for a nice
coloring of my code?

Thanks,

Alan