PR #3286 is now in devel. It restores some legacy functions and fixes a missing alias.Please continue testing. The latest code fixes several brain spikes on my part, but more problems may remain.
This has fixed the g.os_path_join() problem.
I've made copies of the g.os_path_expanduser and g.os_path_join as they existed in Leo 6.7.2. We can't go back to the exact legacy code, but I'll take yet another look after I take a break.
This whole exercise puts me in mind of the several levels of testing: unit, integration, and system. Unit tests can only take you so far. In the case of these os.path-like functions, a unit test could prove that the output equals the intended output, but it could not show that all consuming modules expect the function to act that way.