Add docs for on_failure

Signed-off-by: Keshav Priyadarshi <git@keshav.space>

docs/source/tutorial_add_importer_pipeline.rst

@@ -298,10 +298,14 @@ version management from `univers <https://github.com/aboutcode-org/univers>`_.
     **advisories_count** should never be directly added in steps.
 
 
+.. attention::
+
+   Implement ``on_failure`` to handle cleanup in case of pipeline failure.
+   Cleanup of downloaded archives or cloned repos is necessary to avoid potential resource leakage.
 
 .. note::
 
-   | Use ``make valid`` to format your code using black and isort automatically.
+   | Use ``make valid`` to format your new code using black and isort automatically.
    | Use ``make check`` to check for formatting errors.
 
 Register the Importer Pipeline

docs/source/tutorial_add_improver_pipeline.rst

@@ -187,6 +187,11 @@ methods.
             self.log(f"Successfully flagged {ghost_package_count:,d} ghost Packages")
 
 
+.. attention::
+
+   Implement ``on_failure`` to handle cleanup in case of pipeline failure.
+   Cleanup of downloaded archives or cloned repos is necessary to avoid potential resource leakage.
+
 .. note::
 
    | Use ``make valid`` to format your new code using black and isort automatically.