Comments suggest exceptions are ignore, when in fact they are rethrown

In FeedsSource::import() there is an exception block that ends

catch (Exception $e) {
  // Do nothing.
}

in fact, this exception is being stored and re-thrown after we've had a chance to do some clean up (a bit like a finally block that doesn't require PHP 5.5). The comment (and any similar comments) should be corrected to reflect this.