better debug information

src/rougail/template/base.py

@@ -166,11 +166,14 @@ class RougailExtra:
         try:
             return self.suboption[key]
         except KeyError:
-            raise AttributeError
+            raise AttributeError(f'unable to find extra "{key}"')
 
     def __iter__(self):
         return iter(self.suboption.values())
 
+    def items(self):
+        return self.suboption.items()
+
 
 class RougailBaseTemplate:
     """Engine to process Creole cheetah template
@@ -231,7 +234,7 @@ class RougailBaseTemplate:
 
     def instance_file(self,
                       filevar: Dict,
-                      type: str,
+                      type_: str,
                       service_name: str,
                       ) -> None:
         """Run templatisation on one file
@@ -253,7 +256,7 @@ class RougailBaseTemplate:
                 var = variable[idx]
             else:
                 var = None
-            func = f'_instance_{type}'
+            func = f'_instance_{type_}'
             data = getattr(self, func)(filevar,
                                        filename,
                                        service_name,