Issue with FlowLayout
Tested with PyQt5.14.2 and PySide2 5.13.2

```
In [1]: from silx import sx                                                     
In [2]: from silx.gui.plot.StatsWidget import BasicLineStatsWidget              
In [3]: w = BasicLineStatsWidget(); w.show()                                    
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
TypeError: invalid result from FlowLayout.expandingDirections(), int cannot be converted to PyQt5.QtCore.Orientations in this context
```
diff --git a/silx/gui/widgets/FlowLayout.py b/silx/gui/widgets/FlowLayout.py
index 14c8ab2e0..3c4c9ddce 100644
--- a/silx/gui/widgets/FlowLayout.py
+++ b/silx/gui/widgets/FlowLayout.py
@@ -71,7 +71,7 @@ class FlowLayout(qt.QLayout):
             return None
 
     def expandingDirections(self):
-        return 0
+        return qt.Qt.Orientations()
 
     def hasHeightForWidth(self):
         return True
['silx/gui/widgets/FlowLayout.py']