azure-cli Docker image doesn't support db-up

## Describe the bug

**Command Name**
`az extension add`

**Errors:**
```
An error occurred. Pip failed with status code 1. Use --debug for more information.
```

Attached is the log produced by using the `--debug` flag: [log.txt](https://github.com/Azure/azure-cli/files/6020301/log.txt)

## To Reproduce:

- Launch a docker container using the `mcr.microsoft.com/azure-cli` image.
- `az extension add --name db_up`

## Expected Behavior
The extension installs without error.

## Environment Summary
```
Linux-5.4.0-65-generic-x86_64-with
Python 3.6.10
Installer: DOCKER

azure-cli 2.19.1

```
## Additional Context