ERP5Workflow: use dict comprehension instead of traditional for loop

product/ERP5Workflow/Document/Workflow.py

@@ -763,9 +763,10 @@ class Workflow(IdAsReferenceMixin("", "prefix"), XMLObject, CacheCookieMixin):
     tdef_exprs = {}
     transition_variable_list = []
     if tdef is not None:
-      transition_variable_list = tdef.objectValues(portal_type='Transition Variable')
-    for transition_variable in transition_variable_list:
-      tdef_exprs[transition_variable.getCausalityId()] = transition_variable.getVariableExpression()
+      tdef_exprs = {
+        transition_variable.getCausalityId(): transition_variable.getVariableExpression()
+        for transition_variable in tdef.objectValues(portal_type='Transition Variable')
+      }
 
     # Update all transition variables
     if form_kw is not None: