[cleanup] cleanup scripts/djvutext.py
[cleanup] cleanup scripts/djvutext.py

- use str.format(...) instead of modulo for type specifier
  arguments
- use "+" to concatenate strings in some cases

Change-Id: I45e86cfdfbb625be5ab64c8a12f0e398a3049f41

wikimedia/pywikibot-core,PersianWikipedia/pywikibot-core,wikimedia/pywikibot-core