Jinja template error causes Juju manila-plugin-relation-changed hook to fail

When I try to deploy the stable/yoga release of charm-manila-generic, the charm enters an error state with a failed hook. Here is the traceback from the unit logs for manila-generic/0.

2023-06-30 19:08:34 INFO juju.worker.uniter resolver.go:145 awaiting error resolution for "relation-changed" hook
2023-06-30 19:08:35 INFO unit.manila-generic/0.juju-log server.go:316 manila-plugin:31: Reactive main running for hook manila-plugin-relation-changed
2023-06-30 19:08:35 ERROR unit.manila-generic/0.juju-log server.go:316 manila-plugin:31: Unable to find implementation for relation: requires of juju-info
2023-06-30 19:08:35 INFO unit.manila-generic/0.juju-log server.go:316 manila-plugin:31: Invoking reactive handler: hooks/relations/manila-plugin/provides.py:50:changed
2023-06-30 19:08:35 INFO unit.manila-generic/0.juju-log server.go:316 manila-plugin:31: Invoking reactive handler: reactive/manila_generic_handlers.py:31:send_config
2023-06-30 19:08:35 ERROR unit.manila-generic/0.juju-log server.go:316 manila-plugin:31: Hook error:
Traceback (most recent call last):
  File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/charms/reactive/__init__.py", line 74, in main
    bus.dispatch(restricted=restricted_mode)
  File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/charms/reactive/bus.py", line 390, in dispatch
    _invoke(other_handlers)
  File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/charms/reactive/bus.py", line 359, in _invoke
    handler.invoke()
  File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/charms/reactive/bus.py", line 181, in invoke
    self._action(*args)
  File "/var/lib/juju/agents/unit-manila-generic-0/charm/reactive/manila_generic_handlers.py", line 41, in send_config
    generic_charm.get_config_for_principal(
  File "/var/lib/juju/agents/unit-manila-generic-0/charm/lib/charm/openstack/manila_generic.py", line 204, in get_config_for_principal
    rendered_configs = charmhelpers.core.templating.render(
  File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/charmhelpers/core/templating.py", line 80, in render
    content = template.render(context)
  File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/jinja2/environment.py", line 1291, in render
    self.environment.handle_exception()
  File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/jinja2/environment.py", line 926, in handle_exception
    raise rewrite_traceback_stack(source=source)
  File "templates/mitaka/manila.conf", line 25, in top-level template code
    {% include "parts/authentication_data" %}
  File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/jinja2/environment.py", line 926, in handle_exception
    raise rewrite_traceback_stack(source=source)
  File "templates/parts/authentication_data", line 3, in template
    {{ # Defense mechanism introduced in the charm release 21.10 because of a
jinja2.exceptions.TemplateSyntaxError: unexpected char '#' at 123

2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 Traceback (most recent call last):
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-manila-generic-0/charm/hooks/manila-plugin-relation-changed", line 22, in <module>
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 main()
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/charms/reactive/__init__.py", line 74, in main
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 bus.dispatch(restricted=restricted_mode)
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/charms/reactive/bus.py", line 390, in dispatch
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 _invoke(other_handlers)
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/charms/reactive/bus.py", line 359, in _invoke
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 handler.invoke()
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/charms/reactive/bus.py", line 181, in invoke
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 self._action(*args)
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-manila-generic-0/charm/reactive/manila_generic_handlers.py", line 41, in send_config
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 generic_charm.get_config_for_principal(
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-manila-generic-0/charm/lib/charm/openstack/manila_generic.py", line 204, in get_config_for_principal
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 rendered_configs = charmhelpers.core.templating.render(
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/charmhelpers/core/templating.py", line 80, in render
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 content = template.render(context)
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/jinja2/environment.py", line 1291, in render
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 self.environment.handle_exception()
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/jinja2/environment.py", line 926, in handle_exception
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 raise rewrite_traceback_stack(source=source)
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 File "templates/mitaka/manila.conf", line 25, in top-level template code
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 {% include "parts/authentication_data" %}
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 File "/var/lib/juju/agents/unit-manila-generic-0/.venv/lib/python3.10/site-packages/jinja2/environment.py", line 926, in handle_exception
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 raise rewrite_traceback_stack(source=source)
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 File "templates/parts/authentication_data", line 3, in template
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 {{ # Defense mechanism introduced in the charm release 21.10 because of a
2023-06-30 19:08:35 WARNING unit.manila-generic/0.manila-plugin-relation-changed logger.go:60 jinja2.exceptions.TemplateSyntaxError: unexpected char '#' at 123
2023-06-30 19:08:35 ERROR juju.worker.uniter.operation runhook.go:140 hook "manila-plugin-relation-changed" (via explicit, bespoke hook script) failed: exit status 1

The problem is a typo in the Jinja2 template at templates/parts/authentication_data. It looks like there was supposed to be a comment, but the syntax is incorrect. If you replace

{{ # Defense mechanism introduced in the charm release 21.10 because of a
     relation data key renaming, and would be safe to remove 2 releases later.
#}}

with

{# Defense mechanism introduced in the charm release 21.10 because of a
     relation data key renaming, and would be safe to remove 2 releases later.
#}

The error goes away, the hook fires successfully, and Juju reports a green running status for the manila-generic unit. {# #} is the correct syntax for comments in Jinja2 templates according to the Jinja2 docs at https://jinja.palletsprojects.com/en/3.1.x/templates/#comments.

I will submit a small patch to fix this error in the template and look at backporting it.