Poor error handling merging pdfs incorrectly

[mcoles]

I built a VizAlert to merge a bunch of PDFs, but left off the |filename parameter. The resulting error message was:

The following errors were encountered trying to process your alert:

General errors:

Unable to process task 42eb309e-13ca-460e-a369-1b16b6cf6918 from alert Vizalert, error: filename

We should handle this a little more nicely...

[jdrummey]

One more error related to this. I had a % in the file name (accidentally using a URL-escaped string) and that was not included in the error text.