Just a quick hot fix so that when can still report errors back to the UI even when the task_data can't be serialized, which can happen when functions are defined.

crc/api/common.py

@@ -1,3 +1,5 @@
+import json
+
 from SpiffWorkflow import WorkflowException
 from SpiffWorkflow.exceptions import WorkflowTaskExecException
 from flask import g
@@ -88,6 +90,15 @@ class ApiErrorSchema(ma.Schema):
 @app.errorhandler(ApiError)
 def handle_invalid_usage(error):
     response = ApiErrorSchema().dump(error)
+
+    # In the unlikely event that the API error can't be serialized, try removing the task_data, as it may
+    # contain some invalid data that we can't return, so we can at least get the erro rmessage.
+    try:
+        json_output = json.dumps(response)
+    except TypeError as te:
+        error.task_data = {'task_data_hidden':'We were unable to serialize the task data when reporting this error'}
+        response = ApiErrorSchema().dump(error)
+
     return response, error.status_code