Explanation Cache: add debugging hints

product/ERP5/ExplanationCache.py

@@ -325,6 +325,8 @@ class ExplanationCache:
     try:
       result = cache[reference_date_key]
       if result is self: # use self as marker to detect infinite recursion
+        __traceback_info__ = (business_process.getPath(), trade_phase,
+                              reference_date_method_id, delay_mode)
         raise ValueError('No reference date is defined, probably due to missing Trade Model Path in Business Process')
       return result
     except KeyError: