Add error: True to code cell having AssertionError

Author: rich-iannone

pointblank/validate.py

@@ -5068,6 +5068,8 @@ def assert_passing(self) -> None:
         method is used to assert that all validation steps passed perfectly.
 
         ```{python}
+        #| error: True
+
         import pointblank as pb
         import polars as pl