In both 2.7 and 2.8 register your site, update your registration and unregister your site.
If you need to make your test sites public you can use ngrok.com
To register go to site admin > registration
To unregister go to site admin > server > hubs
Just check that this all works, no missing strings and the test you see makes sense.
MDL-48975 introduced a bunch of string changes and it is fine to go into master. The versions for 2.8 and 2.7 are blocked by MDL-49166 however which is sitting in integration_held.
Once MDL-49166 is integrated the 2.8 and 2.7 versions of MDL-48975 can go up for integration.
is blocked by
MDL-48975Improve messages displayed in the registration process
Closed
MDL-49166Site registration notification (backport of MDL-48894)
Closed
Testing discovered
MDL-49956get_string() calls during registration are receiving parameters the strings don't use