The issue MDL-46267 introduces a final deprecation step for the httpswwwroot and removes it from the core.

However, the setting is still used in many plugins - 201 in the plugins directory. These all will suddenly stop working in 3.8.

We did not have a way to raise a proper deprecation debugging warning when the httpswwwroot is still used. So no-one is really aware about this problem and prepared for it.

I believe we must:

1. re-introduce the httpswwwroot and keep it forever as an alias for the wwwroot.
2. improve the CI tools in the plugins directory and in travis (moodle-plugin-ci) to raise a warning/error when httpswwwroot is found in the plugin's code.