set default python bindings

Author: bergtholdt

ipykernel/eventloops.py

@@ -125,6 +125,8 @@ def loop_qt4(kernel):
 @register_integration('qt', 'qt5')
 def loop_qt5(kernel):
     """Start a kernel with PyQt5 event loop integration."""
+    if os.environ.get('QT_API', None) is None:
+        os.environ['QT_API'] = 'pyqt5'
     return loop_qt4(kernel)