Throwable throwable = (Throwable) Whitebox.getInternalState(failure, "fThrownException");
String newMessage = "contains both: actual test failure *and* Mockito warnings.\n" +
warnings + "\n *** The actual failure is because of: ***\n";
ExceptionIncludingMockitoWarnings e = new ExceptionIncludingMockitoWarnings(newMessage, throwable);
e.setStackTrace(throwable.getStackTrace());
Whitebox.setInternalState(failure, "fThrownException", e);
}