Flag magic usage errors as failures

src/nbmake/nb_run.py

@@ -86,7 +86,11 @@ async def apply_mocks(
 
             c.execute(cwd=self.filename.parent)
         except CellExecutionError:
-            error = self._get_error(nb)
+            error = self._get_error(nb) or NotebookError(
+                summary="An untraced error occurred. This likely was a cell magic (%<command>) usage error",
+                trace="",
+                failing_cell_index=-1,
+            )
         except CellTimeoutError as err:
             trace = err.args[0]
             error = NotebookError(

tests/resources/usageerror.ipynb

@@ -0,0 +1,46 @@
+{
+ "cells": [
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "%fls u908"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "print(4)"
+   ]
+  }
+ ],
+ "metadata": {
+  "interpreter": {
+   "hash": "31f2aee4e71d21fbe5cf8b01ff0e069b9275f58929596ceb00d14d90e3e16cd6"
+  },
+  "kernelspec": {
+   "display_name": "Python 3.8.9 64-bit",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.10.4"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}

tests/test_nb_run.py

@@ -133,3 +133,9 @@ def test_when_empty_then_succeeds(self, testdir2: Never):
         run = NotebookRun(nb, 300)
         res: NotebookResult = run.execute()
         assert res.error is None
+
+    def test_when_usage_error_then_fails(self, testdir2: Never):
+        nb = Path(__file__).parent / "resources" / "usageerror.ipynb"
+        run = NotebookRun(nb, 300)
+        res: NotebookResult = run.execute()
+        assert res.error != None