Summary: The Pymongo client seems to be causing a deadlock when `.close()` is called:

Environment:

• 3.8.12 (default, Jan 15 2022, 18:39:47) [GCC 7.5.0]                            
• Pymongo version: 4.1.1
• Pymongo has c: True

Description:

We've found that any of our scripts that use a utility to wrap a pymongo class won't exit properly. They hang in a deadlock. Ultimately getting stuck trying to restart a monitor thread here.

We've found this started happening for us when upgrading from python 3.6.9 to 3.8.12. We've also found this happens for any python 3.9.* or 3.8.*. 

Impact on us:

This is preventing our company from upgrading from python 3.6.9 which is blocking features we would like to release.

Attached script instructions:

1. Follow the instructions here to install a mongodb server.
2. In a python environment install the attached `pip_deps.txt` list.
3. Run `python example_for_mongo.py`.
4. Watch the script get stuck in deadlock.