Following the instructions in the README and UPGRADING (I think!), I had a number of dependencies to fix.
The make fixdeps was failing on a call to File::Path::rmtree trying to clean up ~/.cpan/build/tmp and the like. I finally got testdeps happy by manually installing the dependencies using cpan.
Then make upgrade ran ok.
BUT it created etc/upgrade/3.5.1 and that directory was empty, so the rt-setup-database commands failed. Trying to run at that point made Bad Things happen (undefined methods and the like), so I backed it out.
I’m probably doing something obviously wrong, but can’t see what it is. Any suggestions?