IMPORTANT: due to a drive failure, as of 13-Mar-2021, the Mercurial repository had to be re-mirrored, which changed every commit SHA. The old SHAs and trees are backed up in the vault branches. Please migrate to the new branches as soon as you can.
Signal handlers work by setting a debug hook. Hooks are per-thread, so we need this to be called in the main thread. However module loading is not in the main thread anymore.