Not what the original poster was asking for, but there is another work around for those not wanting to run a script might be helpful here. I cut and pasted the pdf text into a word processor, then saved the file in an old word doc format -which Scribus can import- and the extra carriage returns were removed. I happen to use home version of Word Perfect, but for the Linux world there are a variety of free word processors.
You probably know this already, but many word processors also allow for making all the tab and carriage returns visible characters so that you can run "find and replace" to get rid of extra spaces, tabs, and carriage returns. To the extent I can, I like to do all the writing and story editing (grammar, spelling, revisions, etc.) in a word processor, then pull that into Scribus.