auth emulator for extensions doesn't run

[russellwheatley]

[REQUIRED] Environment info

firebase-tools:
8.17.0

Platform:
macOS Catalina 10.15.4

[REQUIRED] Test case

See steps to reproduce.

[REQUIRED] Steps to reproduce

1. git clone git@github.com:firebase/extensions.git
2. run npm i from root of extension's directory.
3. cd delete-user-data directory
4. create test-params.env file. Add environment variables & insert project id as appropriate:

LOCATION=europe-west2
STORAGE_PATHS={DEFAULT}/test/{UID}-test.png
SELECTED_DATABASE_INSTANCE=[INSERT YOUR OWN PROJECT ID]
FIRESTORE_DELETE_MODE=shallow

5. delete line 159: default: ${DATABASE_INSTANCE} & validationRegex: ^([0-9a-z_.-]*)$ from the extension.yaml file otherwise you will encounter the issue I raised here.
6. run CLI command with your project id : firebase ext:dev:emulators:start --test-params=test-params.env --project=[INSERT YOUR OWN PROJECT ID]

[REQUIRED] Expected behavior

I expect to have Cloud Function and Auth emulators running.

[REQUIRED] Actual behavior

The auth emulator does not run: