test: failing reproducer - snap developer-id not asserted

[lengau]

Reproducer for #445

When a snap changes ownership (e.g. transferred from a personal account to an org), the snap-revision assertion contains a developer-id that differs from the current publisher. The current code only asserts the publisher's account, not the developer's, causing snap ack to fail with:

error: cannot assert: assert failed: cannot resolve prerequisite assertion: account (<developer-id>)

Root cause

_get_assertions_file() in snap_installer.py always queries account-id=<publisher_id> but never reads the developer-id field from the snap-revision assertion bytes to also fetch account-id=<developer-id>.

Fix

Parse the snap-revision assertion to extract developer-id. If it differs from the publisher-id, also fetch ["account", "account-id=<developer-id>"] and include it in the assertion file.

Closes #445

[lengau]

@copilot create a fix that causes the test to pass and fixes #445

[Copilot]

@copilot create a fix that causes the test to pass and fixes #445

Fixed in 5df1922. The change modifies _get_assertions_file() in snap_installer.py to:

1. Fetch the snap-revision assertion first and parse its developer-id field
2. If developer-id differs from the publisher-id, also fetch an account assertion for the developer

A helper _get_developer_id_from_snap_revision() handles the byte parsing with safe UnicodeDecodeError handling. All 37 unit tests for snap_installer pass.