Flask docker image

A variant of my uWSGI docker image with some extra features for Flask:

• Automatically sets FLASK_APP environment variable to the value of WSGI_MODULE.
• Add "shell" entry point, which drops the user into a Flask shell - a REPL with your application module pre-imported. Simply run docker run -ti cheaterman/flask shell to use it.

Both are particularly useful features to run maintenance scripts in general, such as for handling DB migrations.

See also: Docker Hub repository