Since https://gerrit.wikimedia.org/r/#/c/328292/ , a "twn" branch is supposed to exist on the repository, so that l10n updates can be fetched and new translations exported. The branch needs to be kept in sync with the main branch by the repository administrators.
Exports are failing most of the time because the branch doesn't actually exist. Please make sure it always does, or let us export to master/develop.