"management-console: ... Failed to migrate the DB... can’t acquire database lock" during upgrade from 3.2.1 to 3.4.1

Created by: dadlerj

• Sourcegraph version: Upgrading from 3.2.1 to 3.4.1
• Platform information:

Steps to reproduce:

Reported by https://app.hubspot.com/contacts/2762526/company/887065580

My process:

1. Stop Sourcegraph 3.2.1
2. Pull and start Sourcegraph 3.4.1
3. I saw the following error and Sourcegraph failed to startup

16:06:09 management-console | 2019/05/24 16:06:09 Fatal error connecting to Postgres DB: Failed to migrate the DB. Please contact support@sourcegraph.com for further assistance: timeout: can’t acquire database lock

Expected behavior:

Successful upgrade

Actual behavior:

Failed upgrade