FEM: some Python constraint VP, add import of FemGui to get the icon in TreeView when there is no analysis and Fem is not loaded

src/Mod/Fem/femguiobjects/ViewProviderFemConstraint.py

@@ -29,6 +29,9 @@ __url__ = "http://www.freecadweb.org"
 
 import FreeCAD
 import FreeCADGui
+import FemGui  # needed to display the icons in TreeView
+False if False else FemGui.__name__  # dummy usage of FemGui for flake8, just returns 'FemGui'
+
 from pivy import coin
 
 

src/Mod/Fem/femguiobjects/_ViewProviderFemConstraintSelfWeight.py

@@ -29,6 +29,8 @@ __url__ = "http://www.freecadweb.org"
 
 import FreeCAD
 import FreeCADGui
+import FemGui  # needed to display the icons in TreeView
+False if False else FemGui.__name__  # dummy usage of FemGui for flake8, just returns 'FemGui'
 
 
 class _ViewProviderFemConstraintSelfWeight:

src/Mod/Fem/femguiobjects/_ViewProviderFemElementFluid1D.py

@@ -30,7 +30,8 @@ __url__ = "http://www.freecadweb.org"
 
 import FreeCAD
 import FreeCADGui
-
+import FemGui  # needed to display the icons in TreeView
+False if False else FemGui.__name__  # dummy usage of FemGui for flake8, just returns 'FemGui'
 
 # for the panel
 from femobjects import _FemElementFluid1D

src/Mod/Fem/femguiobjects/_ViewProviderFemElementGeometry1D.py

@@ -29,7 +29,8 @@ __url__ = "http://www.freecadweb.org"
 
 import FreeCAD
 import FreeCADGui
-
+import FemGui  # needed to display the icons in TreeView
+False if False else FemGui.__name__  # dummy usage of FemGui for flake8, just returns 'FemGui'
 
 # for the panel
 from femobjects import _FemElementGeometry1D

src/Mod/Fem/femguiobjects/_ViewProviderFemElementGeometry2D.py

@@ -29,7 +29,8 @@ __url__ = "http://www.freecadweb.org"
 
 import FreeCAD
 import FreeCADGui
-
+import FemGui  # needed to display the icons in TreeView
+False if False else FemGui.__name__  # dummy usage of FemGui for flake8, just returns 'FemGui'
 
 # for the panel
 from PySide import QtCore

src/Mod/Fem/femguiobjects/_ViewProviderFemElementRotation1D.py

@@ -29,6 +29,8 @@ __url__ = "http://www.freecadweb.org"
 
 import FreeCAD
 import FreeCADGui
+import FemGui  # needed to display the icons in TreeView
+False if False else FemGui.__name__  # dummy usage of FemGui for flake8, just returns 'FemGui'
 
 # for the panel
 from PySide import QtCore

src/Mod/Fem/femguiobjects/_ViewProviderFemMaterial.py

@@ -29,7 +29,8 @@ __url__ = "http://www.freecadweb.org"
 
 import FreeCAD
 import FreeCADGui
-
+import FemGui  # needed to display the icons in TreeView
+False if False else FemGui.__name__  # dummy usage of FemGui for flake8, just returns 'FemGui'
 
 # for the panel
 from FreeCAD import Units

src/Mod/Fem/femguiobjects/_ViewProviderFemMaterialMechanicalNonlinear.py

@@ -29,6 +29,9 @@ __url__ = "http://www.freecadweb.org"
 
 import FreeCAD
 import FreeCADGui
+import FemGui  # needed to display the icons in TreeView
+False if False else FemGui.__name__  # dummy usage of FemGui for flake8, just returns 'FemGui'
+
 from pivy import coin
 
 

src/Mod/Fem/femguiobjects/_ViewProviderFemMeshBoundaryLayer.py

@@ -29,7 +29,8 @@ __url__ = "http://www.freecadweb.org"
 
 import FreeCAD
 import FreeCADGui
-
+import FemGui  # needed to display the icons in TreeView
+False if False else FemGui.__name__  # dummy usage of FemGui for flake8, just returns 'FemGui'
 
 # for the panel
 from PySide import QtCore

src/Mod/Fem/femguiobjects/_ViewProviderFemMeshGmsh.py

@@ -31,7 +31,6 @@ import FreeCAD
 import FreeCADGui
 import FemGui
 
-
 # for the panel
 from femobjects import _FemMeshGmsh
 from PySide import QtCore

src/Mod/Fem/femguiobjects/_ViewProviderFemMeshGroup.py

@@ -29,7 +29,8 @@ __url__ = "http://www.freecadweb.org"
 
 import FreeCAD
 import FreeCADGui
-
+import FemGui  # needed to display the icons in TreeView
+False if False else FemGui.__name__  # dummy usage of FemGui for flake8, just returns 'FemGui'
 
 # for the panel
 import femmesh.meshtools as FemMeshTools

src/Mod/Fem/femguiobjects/_ViewProviderFemMeshRegion.py

@@ -29,7 +29,8 @@ __url__ = "http://www.freecadweb.org"
 
 import FreeCAD
 import FreeCADGui
-
+import FemGui  # needed to display the icons in TreeView
+False if False else FemGui.__name__  # dummy usage of FemGui for flake8, just returns 'FemGui'
 
 # for the panel
 import femmesh.meshtools as FemMeshTools

src/Mod/Fem/femguiobjects/_ViewProviderFemResultMechanical.py

@@ -30,7 +30,8 @@ __url__ = "http://www.freecadweb.org"
 
 import FreeCAD
 import FreeCADGui
-
+import FemGui  # needed to display the icons in TreeView
+False if False else FemGui.__name__  # dummy usage of FemGui for flake8, just returns 'FemGui'
 
 # for the panel
 import FemGui

src/Mod/Fem/femguiobjects/_ViewProviderFemSolverCalculix.py

@@ -31,7 +31,6 @@ import FreeCAD
 import FreeCADGui
 import FemGui
 
-
 # for the panel
 from femtools import ccxtools
 from PySide import QtCore