I just tried upgrading our discourse forum and a little ways into the installation I got this error:
I updated the the Ruby version in the docker container to Ruby 2.4.4 and set it to the default version using RVM, The default version then showed Ruby 2.4.4 (was 2.3.3). I retried the upgrade and got the same message as in the screen shot above.
I logged out of the docker container and tried a ./launcher rebuild app. After a painfully long time the rebuild failed with the same error message:
I had to completely reinstall Docker with a wget (found the command in the forum) then run the launcher rebuild twice (not because of errors, instructions during the install said to do that). Now have the latest version of docker, postgres, and the forum, best of all I don’t seem to have lost any data and I can login to the forum. Oh, also like all the pretty new graphs in the admin section.