docs: def run(self):
          """Called when a file is changed to re-run the tests with nose."""
          if self.auto_clear:
              os.system('cls' if os.name == 'nt' else 'auto_clear')
          else:
              print
          print 'Running unit tests...'
          if self.auto_clear:
              print
          subprocess.call('nosetests', cwd=self.directory)