code: def update_wsnum_in_files(self, vernum):
          
          self.version_num = vernum
          # replace the WSNUMBER in the url paths with the real WS###
          for f in self.files:
              url = self.files[f].get('url')
              url = re.sub(r'WSNUMBER', self.version_num, url)
              self.files[f]['url'] = url
              LOG.debug(
                  "Replacing WSNUMBER in %s with %s", f, self.version_num)
  
          # also the letter file - keep this so we know the version number
          # self.files['checksums']['file'] = re.sub(
          #    r'WSNUMBER', self.version_num, self.files['checksums']['file'])
          return
docs: With the given version number ```vernum```,
          update the source's version number, and replace in the file hashmap.
          the version number is in the CHECKSUMS file.
          :param vernum:
          :return: