For each of the languages do the specified actions from below.
(Note: This is a fix for the Error: HTS_Model_load_pdf: Failed to load header of pdfs
For more info check here https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=589614):
Modify the the following parts of the *_ths.scm file for each of the language (e.g. /usr/share/festival/voices/us/nitech_us_awb_arctic_hts/festvox/nitech_us_awb_arctic_hts.scm)
(require 'hts) (require_module 'hts_engine)
change to (require 'hts21compat) (require_module 'hts21_engine)
(Parameter.set 'Synth_Method 'HTS)
change to (Parameter.set 'Synth_Method 'HTS21)