Internal error: PT reactor closed unexpectedly

When playing with obfs4proxy:

2022-11-30T14:32:32.783212Z  INFO tor_circmgr::mgr: While waiting on circuit: Ok(Err(Channel { peer: [scrubbed], cause: Pt(Internal(Bug(BugRepr { message: "PT reactor closed unexpectedly", location: Location { file: "/home/nickm/src/arti/crates/tor-ptmgr/src/lib.rs", line: 453, col: 52 }, backtrace: Captured(   0: tor_error::internal::Bug::new_inner
   1: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   2: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   3: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   4: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   5: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   6: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   7: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   8: tokio::runtime::task::raw::poll
   9: tokio::runtime::scheduler::multi_thread::worker::Context::run_task
  10: tokio::runtime::task::raw::poll
  11: tokio::runtime::task::UnownedTask<S>::run
  12: std::sys_common::backtrace::__rust_begin_short_backtrace
  13: core::ops::function::FnOnce::call_once{{vtable.shim}}
  14: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/alloc/src/boxed.rs:1940:9
      <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/alloc/src/boxed.rs:1940:9
      std::sys::unix::thread::Thread::new::thread_start
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/sys/unix/thread.rs:108:17
  15: start_thread
  16: __GI___clone3
), source: None, kind: Internal }))) })) from circuit we're building
2022-11-30T14:32:32.783249Z  INFO tor_circmgr::mgr: While waiting on circuit: Ok(Err(Channel { peer: [scrubbed], cause: Pt(Internal(Bug(BugRepr { message: "PT reactor closed unexpectedly", location: Location { file: "/home/nickm/src/arti/crates/tor-ptmgr/src/lib.rs", line: 453, col: 52 }, backtrace: Captured(   0: tor_error::internal::Bug::new_inner
   1: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   2: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   3: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   4: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   5: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   6: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   7: <core::future::from_generator::GenFuture<T> as core::future::future::Future>::poll
   8: tokio::runtime::task::raw::poll
   9: tokio::runtime::scheduler::multi_thread::worker::Context::run_task
  10: tokio::runtime::task::raw::poll
  11: tokio::runtime::task::UnownedTask<S>::run
  12: std::sys_common::backtrace::__rust_begin_short_backtrace
  13: core::ops::function::FnOnce::call_once{{vtable.shim}}
  14: <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/alloc/src/boxed.rs:1940:9
      <alloc::boxed::Box<F,A> as core::ops::function::FnOnce<Args>>::call_once
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/alloc/src/boxed.rs:1940:9
      std::sys::unix::thread::Thread::new::thread_start
             at /rustc/897e37553bba8b42751c67658967889d11ecd120/library/std/src/sys/unix/thread.rs:108:17
  15: start_thread
  16: __GI___clone3
), source: None, kind: Internal }))) })) from circuit we're building
2022-11-30T14:32:32.783307Z  INFO tor_circmgr::mgr: Circuit attempt 1 failed.

cc @eta