Test does not raise on yield but "???" prints

test.py

from unittest import TestCase

from nose.tools import raises
from nose.twistedtools import reactor
from twisted.internet.defer import inlineCallbacks
from twisted.internet.threads import blockingCallFromThread

class TestExample(TestCase):
  @inlineCallbacks
  @raises(RuntimeError)
  def test_raise(self):
      def raiseError():
          raise RuntimeError()
  
      def crash():
          print "test"
          yield raiseError()
  
      try:
          bla = yield blockingCallFromThread(reactor, crash)
          bla.next()
      except RuntimeError:
          print "???"
          raise