Deleting unevaluated `@lazy` attribute raises KeyError

[Peter Suter]

When the @lazy decorator is used, previously evaluated attributes can be invalidated to force re-evaluation using del.

However in case the attribute had not been previously evaluated this raises a KeyError:

ERROR: For backward compatibility with plugin, upgrade with a `db`

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Traceback (most recent call last):

File "/home/travis/build/edgewall/trac/trac/tests/env.py", line 177, in test_upgrade_legacy_participant

self.assertTrue(self.env.upgrade())

File "/home/travis/build/edgewall/trac/trac/env.py", line 768, in upgrade

del self.database_version

File "/home/travis/build/edgewall/trac/trac/util/__init__.py", line 1151, in __delete__

del instance.__dict__[self.fn.__name__]

KeyError: 'database_version'

This was previously discussed in comment:30:ticket:8172 and following.

changeset:13927 was committed to fix the broken unit test.

[Peter Suter]

Replying to rjollos:

I wonder if it would be a good idea to backport [13927] to 1.0-stable.

Feel free to retarget.

[Ryan J Ollos]

We can probably just backport to 1.0-stable later if needed.

[Peter Suter]

Sounds good, thanks.