Fix test failures on Python 3.14 (#394)

* Fix test failures on Python 3.14

As documented at
https://docs.python.org/3/library/asyncio-eventloop.html#asyncio.get_event_loop,
`get_event_loop` now fails if there is no active event loop. Since there
will never already be one at the top level of a file anyway, explicitly
create a new one every time.

* Reformat with black 2026 style

setup.py

@@ -21,7 +21,6 @@ sys.path.insert(1, _this_dir)
 from buildutils.build import build_libcapnp
 from buildutils.bundle import fetch_libcapnp
 
-
 MAJOR = 2
 MINOR = 2
 MICRO = 2