Skipped 'daa8b7f61' from master: catch and report TTS errors (#5561)

* catch and report TTS errors

implement onError() to report a Toast with some hints to the user
in case the TTS engine returns an error.

From API 21 upwards we would also have the error code available
for further details on what happened.

* Display Snackbar for failing TTS

In case TTS output fails display a Snackbar with an error
message and a help link pointing to the FAQ with recovery
instructions.