don't use CacheFileManager.__del__ on interpreter shutdown (#7880)

* store a reference to the acquire function on the object

This keeps the function from being garbage collected before we can
call it.

* whats-new.rst

* make `lock_acquire` a static method

* fix rst link

* comment on the existence of the static method `lock_acquire`

* also store a reference to `OPTIONS`

* revert storing additional references

* remove `CachingFileManager.__del__` on interpreter shutdown

* rephrase the changelog [skip-ci]

* [skip-ci]

---------

Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>

Author: keewis

doc/whats-new.rst

@@ -42,7 +42,8 @@ Performance
 
 Bug fixes
 ~~~~~~~~~
-
+- Don't call ``CachingFileManager.__del__`` on interpreter shutdown (:issue:`7814`, :pull:`7880`).
+  By `Justus Magin <https://github.com/keewis>`_.
 
 Documentation
 ~~~~~~~~~~~~~

xarray/backends/file_manager.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import atexit
 import contextlib
 import io
 import threading
@@ -289,6 +290,13 @@ def __repr__(self) -> str:
         )
 
 
+@atexit.register
+def _remove_del_method():
+    # We don't need to close unclosed files at program exit, and may not be able
+    # to, because Python is cleaning up imports / globals.
+    del CachingFileManager.__del__
+
+
 class _RefCounter:
     """Class for keeping track of reference counts."""