Handle errors

Author: chrisjsewell

nbclient/client.py

@@ -1086,7 +1086,7 @@ async def async_execute_expressions(self, cell, cell_index: int, expressions: t.
             finally:
                 raise
         self._check_raise_for_error(cell, exec_reply)
-        attachments = {key: val["data"] for key, val in exec_reply["content"]["user_expressions"].items()}
+        attachments = {key: val["data"] if "data" in val else {"traceback": "\n".join(val["traceback"])} for key, val in exec_reply["content"]["user_expressions"].items()}
         cell.setdefault("attachments", {})
         # remove old expressions from cell
         cell["attachments"] = {key: val for key, val in cell["attachments"].items() if not key.startswith(MD_EXPRESSIONS_PREFIX)}

nbclient/tests/files/Markdown_expressions.ipynb

@@ -15,12 +15,13 @@
    "metadata": {},
    "attachments": {
     "md-expr-0": {"text/plain": "1"},
-    "md-expr-1": {"text/plain": "'c'"}
+    "md-expr-1": {"text/plain": "'c'"},
+    "md-expr-2": {"traceback": "\u001b[0;31mNameError\u001b[0m\u001b[0;31m:\u001b[0m name 'c' is not defined\n"}
    },
    "source": [
     "# Variables\n",
     "\n",
-    "{{ a }} {{ b }}"
+    "{{ a }} {{ b }} {{ c }}"
     ]
   }
  ],