available mappings message

src/tag_converter.py

@@ -26,7 +26,8 @@ class TagConverter(nlp_ws.NLPWorker):
             mapping = self.mappings[task_options.get('mapping')]
             reg = re.compile(r'<ctag>.*</ctag>')
         except KeyError as e:
-            raise Exception('Unknown mapping: ' + task_options.get('mapping'))
+            raise Exception('Unknown mapping: ' + task_options.get('mapping')
+                            + "\nAvailable mappings: " + str(self.mappings.keys()))
         with open(input_file, "rt") as f:
             lines = f.readlines()
             newlines = []