Update bug_931 unit test to check for isinstance.
Update bug_931 unit test to check for isinstance.

Reviewer: Luciano Wolf <c353ae890f0e6de8473e43011f009ccd38a3c452@openbossa.org>
          Lauro Neto <lauro.neto@openbossa.org>

M4rtinK/pyside-android,enthought/pyside,gbaty/pyside2,PySide/PySide,BadSingleton/pyside2,RobinD42/pyside,M4rtinK/pyside-bb10,M4rtinK/pyside-bb10,RobinD42/pyside,qtproject/pyside-pyside,RobinD42/pyside,RobinD42/pyside,enthought/pyside,PySide/PySide,M4rtinK/pyside-android,BadSingleton/pyside2,RobinD42/pyside,M4rtinK/pyside-android,M4rtinK/pyside-android,M4rtinK/pyside-bb10,M4rtinK/pyside-bb10,qtproject/pyside-pyside,BadSingleton/pyside2,pankajp/pyside,enthought/pyside,RobinD42/pyside,qtproject/pyside-pyside,gbaty/pyside2,qtproject/pyside-pyside,PySide/PySide,pankajp/pyside,BadSingleton/pyside2,pankajp/pyside,IronManMark20/pyside2,pankajp/pyside,IronManMark20/pyside2,enthought/pyside,IronManMark20/pyside2,BadSingleton/pyside2,PySide/PySide,M4rtinK/pyside-bb10,gbaty/pyside2,enthought/pyside,M4rtinK/pyside-bb10,M4rtinK/pyside-android,M4rtinK/pyside-android,qtproject/pyside-pyside,gbaty/pyside2,enthought/pyside,enthought/pyside,RobinD42/pyside,pankajp/pyside,PySide/PySide,IronManMark20/pyside2,IronManMark20/pyside2,gbaty/pyside2