Comment 0 for bug 1897778

In order for custom PostInstallScript to add/remove apt packages and call apt update, DistUpgradecontroller needs to release the apt cache directory lock before that stage.

If the lock is still in place, DistUpgradeController.runPostUpgradeScripts hits errors such as:

E: Could not get lock /var/lib/apt/lists/lock - open (11: Resource temporarily unavailable)
E: Unable to lock directory /var/lib/apt/lists/