Bug#3107 Document use of tmp_filename. The caller needs to clean upthe tmp file. The content repository does not "know" what the properprocedure is to handle the file.
Made sure we are not returning something for the portrait if it was not found as this confuses the load balancer. I personally think we should not return the error message, especially as the portrait-bits are usually included as an image in OpenACS, which makes the error senseless anyway