Anti-spam check on Sequence Export plugin.
PubMLST has been seeing lots of automated attempts to post spam using
the sequence export page.  HTML links have been pasted in to the text
box used to upload lists of STs or isolate ids for export.  While this
didn't result in any spam, it did send the job to the job queue where
the offline job manager then rejected the job due to no valid data.  We
now reject jobs with HTML links in the data prior to sending to the job
queue.