This is a follow up to the repository based coursier integration. The
standard coursier integration is to this integration what the docker
integration is to the docker_image integration.
This is meant to target either maven coordinates or coursier apps
directly without depending on a hook repository containing app
descriptors and hook configs making this integration highly suitable
for local hooks.
An example of hook local targets are bellow
```yaml
- repo: local
hooks:
- id: scalafmt
name: scalafmt
entry: scalafmt # coursier app target
language: coursier_launch
files: (\.scala|\.sbt|\.sc)$
- id: scalafix
name: scalafix
entry: ch.epfl.scala:::scalafix-cli:latest.release # maven coordinates target
language: coursier_launch
files: (\.scala|\.sbt|\.sc)$
- id: echo-java
name: echo-java
entry: echo-java
language: coursier_launch
args: ["--", "hello from java"] # forward arguments to the app
```
- the `healthy()` check now requires virtualenv 20.x's metadata
- `python_venv` is obsolete now that `virtualenv` generates the same structure
and `virtualenv` is more portable
`docker_image` is intended to be a lightweight hook type similar to system /
script which allows one to use an existing docker image which provides a
hook.
