//extdist.wmflabs.org/dist/extensions/TinyMCE-REL1_31-0717546.tar.gz doesn't contain any files...
Topic on Extension talk:ExtensionDistributor
Yes, the repo didn't really exist at that point: https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/extensions/TinyMCE/+log/refs/heads/REL1_31