Resolve "Provide docs to help with migration Debian 10 -> 11"

changes/changelog.d/1562.doc

@@ -0,0 +1 @@
+Added virtualenv upgrade instructions for Debian (#1562).

docs/administrator_documentation/installation_docs/debian.md

@@ -15,11 +15,11 @@ We support [Debian](https://debian.org) and Debian-based Linux distributions. Fo
    export FUNKWHALE_VERSION={sub-ref}`version`
    ```
 
-- Install `curl` and `unzip` - utilities used later.
+- Install `curl`
 
    ```{code} bash
    sudo apt update # update apt cache
-   sudo apt install curl unzip
+   sudo apt install curl
    ```
 
 ## 1. Install Funkwhale dependencies

docs/administrator_documentation/upgrade_docs/debian.md

@@ -2,6 +2,28 @@
 
 If you installed Funkwhale following the [Debian guide](../installation_docs/debian), follow these steps to upgrade.
 
+:::{dropdown} Upgrading to a new version of Python
+:icon: alert
+:color: warning
+
+If you upgrade your Python version, you need to update your virtualenv. Python is updated with each new version of Debian.
+
+To upgrade your virtualenv:
+
+1. Change to your api directory.
+
+   ```{code-block} bash
+   cd /srv/funkwhale/api
+   ```
+
+2. Rerun `poetry install` to reinstall your dependencies in a new virtualenv.
+
+   ```{code-block} bash
+   poetry install
+   ```
+
+:::
+
 ## Download the updated files
 
 1. SSH into your server.