Fix "Canceled by user" messagebox (wasn't intended to pop up)

lattice2Common.py

@@ -22,6 +22,7 @@
 #***************************************************************************
 
 import FreeCAD, Part
+from latticeExecuter import CancelError
 if FreeCAD.GuiUp:
     import FreeCADGui
     from PySide import QtCore, QtGui
@@ -57,6 +58,8 @@ class SelectionError(FreeCAD.Base.FreeCADError):
         self.title = title
         
 def msgError(err):
+    #if type(err) is CancelError: return   # doesn't work! Why!
+    if hasattr(err, "isCancelError") and err.isCancelError: return   #workaround
     mb = QtGui.QMessageBox()
     mb.setIcon(mb.Icon.Warning)
     mb.setText(err.message)

lattice2Executer.py

@@ -94,4 +94,5 @@ def _showMsg(obj, message, _type):
 
 class CancelError(Exception):
     def __init__(self):
-        self.message = "Canceled by user"
+        self.message = "Canceled by user"
+        self.isCancelError = True