Py3: fix "err has no attribute message"

lattice2Common.py

@@ -55,6 +55,7 @@ class SelectionError(FreeCAD.Base.FreeCADError):
     '''Error that isused inside Gui command code'''
     def __init__(self, title, message):
         self.message = message
+        self.args = (message,)
         self.title = title
         
 def msgError(err):
@@ -62,7 +63,7 @@ def msgError(err):
     if hasattr(err, "isCancelError") and err.isCancelError: return   #workaround
     mb = QtGui.QMessageBox()
     mb.setIcon(mb.Icon.Warning)
-    mb.setText(err.message)
+    mb.setText(str(err))
     if type(err) is SelectionError:
         mb.setWindowTitle(err.title)
     else:

lattice2Subsequencer.py

@@ -378,7 +378,7 @@ def Subsequence_LinkDict(link_dict, traversal = TRAVERSAL_MODES[0], loop = LOOP_
     # trim them to shortest subsequence
     if n_seq is None:
         raise SubsequencingError_LinkValue("In supplied links, nothing to loop over compounds was found. Key-by-key errors follow: {err_list}"
-          .format(err_list= "\n".join([repr(key)+": "+err_dict[key].message for key in err_dict])))
+          .format(err_list= "\n".join([repr(key)+": "+str(err_dict[key]) for key in err_dict])))
     for key in ret_dict.keys():
         seq = ret_dict[key]
         seq = seq[0:n_seq]