python requirements: licenses should be documented

[0xc0170]

Description

@fkjagodzinski made a good point about the python module licenses.

We have requirements.txt: https://github.com/ARMmbed/mbed-os/blob/master/requirements.txt . No documentation for licenses of these modules. Our tools depend on these, should be part of the license file.

hidapi module for instance can be used under one of 3 licenses, we should choose one and document it.

https://github.com/ARMmbed/mbed-os/blob/master/LICENSE.md - this should capture our requirements licenses.

Issue request type

[ ] Question
[ ] Enhancement
[X] Bug

[0xc0170]

cc @ARMmbed/mbed-os-tools

[ciarmcom]

Internal Jira reference: https://jira.arm.com/browse/MBOCUSTRIA-1012

[theotherjimmy]

Yep. Sure.