[0.8.0] Custom Logo does not persist with upgrade

[emkll]

Description

The optional custom logo that is on source and journalist interfaces is not preserved when the instance is upgraded from0.7.0 to 0.8.0. It is replaced with the default SecureDrop logo.

Steps to Reproduce

1. Install SecureDrop 0.7.0 in prod vms
2. Upload a custom Instance Logo
3. Upgrade to SecureDrop 0.8.0~rc1
4. Navigate to the Source interface and observe the default logo.

Expected Behavior

Upgrading to 0.8.0 should preserve the custom instance logo.

Actual Behavior

The custom logo is replaced by the default SecureDrop logo.

Comments

There are no apparmor/grsecurity errors, it seems like app code packaging/upgrade logic.
The custom logo is no longer found in /var/www/securedrop/static/i/

Workaround

Admin can run the install playbook to re-upload the image.

[heartsucker]

Related: #2807, #3057, #3219

[emkll]

This is due to an error on my part when building the debs: I had a local version of securedrop/static/i/custom_logo.png in the repo, which overrides the server version. Debs have been updated and I have confirmed the issue no longer persists.