Fix isort, add newsfragment

newsfragments/2700.misc.rst

@@ -0,0 +1,4 @@
+Trio now indicates its presence to `sniffio` using the ``sniffio.thread_local``
+interface that is preferred since sniffio v1.3.0. This should be less likely
+than the previous approach to cause :func:`sniffio.current_async_library` to
+return incorrect results due to unintended inheritance of contextvars.

trio/_util.py

@@ -10,9 +10,10 @@
 from abc import ABCMeta
 from functools import update_wrapper
 
-import trio
 from sniffio import thread_local as sniffio_loop
 
+import trio
+
 # Equivalent to the C function raise(), which Python doesn't wrap
 if os.name == "nt":
     # On Windows, os.kill exists but is really weird.