message: raise a typed exception for unpacker when unknown secondary dex mode is encountered
  Summary: Redex: adding this exception in order to distinguish this error in caller.
diff: @@ -497,11 +497,15 @@ SECONDARY_DEX_MODES = [
  ]
  +class UnknownSecondaryDexModeException(Exception):
  + pass
  +
  +
  def detect_secondary_dex_mode(extracted_apk_dir):
  for mode in SECONDARY_DEX_MODES:
  if mode.detect(extracted_apk_dir):
  return mode
  - raise Exception('Unknown secondary dex mode')
  + raise UnknownSecondaryDexModeException()
  def extract_dex_from_jar(jarpath, dexpath):
  