message: HTTPDownload: Drop capital letter in error message.
diff: @@ -4157,7 +4157,7 @@ class HTTPDownload(Builder):
  break
  if response is None:
  raise Exception(
  - 'Unable to download {}'.format(
  + 'unable to download {}'.format(
  pretty_listing(
  self.__urls, any = True, quantifier = True)))
  return response.status_code, response.content
  