code: public static Exception rethrowAsException(Throwable e) throws Exception {
          Throwables.<Exception>rethrow(e);
          return null; // we never get here
      }
docs: Rethrows the given {@code Throwable}, allowing the caller to
  declare that it throws {@code Exception}. This is useful when
  your callers have nothing reasonable they can do when a
  {@code Throwable} is thrown. This is declared to return {@code Exception}
  so it can be used in a {@code throw} clause:
  <pre>
  try {
  doSomething();
  } catch (Throwable e} {
  throw Throwables.rethrowAsException(e);
  }
  doSomethingLater();
  </pre>
  
  @param e exception to rethrow
  @return does not return anything
  @since 4.12