Move edx-sandbox requirements to codejail-includes

Context

"edx-sandbox" is the environment in which user-authored edx-platform code is safely executed using the codejail library. Today, the edx-sandbox environment's requirements are installed from edx-platform.

One of its requirements is codejail-includes, which contains code that was formerly stored in edx-platform. We extracted it out so that the edx-platform and edx-sandbox Python versions could be managed independently. Please note: the standard edx-platform environment also installs codejail-includes so that user-authored code can be unsafely executed in tests and development.

We find ourselves wishing that we could offer multiple versions of the edx-sandbox environment. This would allow site operators test out, jump ahead, or lag on edx-sandbox updates (probably just Python and library upgrades, but maybe one day API changes) separate from their regular release upgrades. It would allow us to give site operators advance notice on edx-sandbox environment changes and ask that some operators try out new edx-sandbox environments ahead of named releases.

We see two ways to do this:

1. Stick more .in files into the edx-platform edx-sandbox requirements folder. Operators would choose different edx-sandbox versions by pip-r-installing different .txt files in that directory.
2. Move everything from edx-platform edx-sandbox requirements to be requirements of codejail-includes, allowing us to get those edx-sandbox requirements lists out of edx-platform. Ideally, the list in codejail-includes should be a new .in file, so that it is clear that these packages are not required by the actual code within codejail-includes. The generated .txt file would be included into edx-sandbox's base.in. That way, operators would choose different edx-sandbox versions by pointing at different versions of codejail-includes.

I think 2 is a more elegant solution.

Tasks

• Confirm that approach 2 will work
• (Add steps for extraction)
• Delete https://github.com/openedx/edx-platform/tree/master/requirements/edx-sandbox

TBD

Start by comparing edx-platform's requirements/edx-sandbox directory with codejail-includes' requirements directory and read the linked codejail-includes extraction context. Confirm whether the proposed requirements move and version selection work, document the extraction steps, and remove the edx-sandbox requirements directory if the approach is viable.