Recent `swh-web` dependencies upgrade broke the tests:
- pip new resolver and its backtracking process now ends up installing `pybadges 1.0` instead of `pybadges 2.2.1` (I did not look at the details but some transitive dependencies must have pinned pybadges version)
- `django-webpack-loader 1.0` got released, it expects a JSON schema for the webpack stats file different than in previous releases
That diff fixes all new errors that were raised since these depencencies upgrade.
`django-webpack-loader 1.0` is not packaged in debian and will surely be not distributed in `buster`
so we will have to package it ourself (package is quite lightweight so this should not be too
complicated to do).