I was a bit surprised that deque is implemented as a linked list and not, for example, a ring buffer. It would mean that index reads would be constant time (though insert and delete at an index would be linear time), the opposite of using a linked list.
pip is a perfectly usable package manager and is included in most python distributions now. Is it perfect? No, but it is good enough for every team I have been on.
Why should we keep leap seconds? Let noon drift by 1 minute per century (or whatever).
They forgot the Erlang approach: throw exceptions but never catch them. If you are throwing an exception either your code is wrong or your system is bad. In either case, you should crash violently and let another instance handle the retry.
I am used to seeing ring buffers implemented using an array. They are FIFO if you write to the maximum offset and read from the minimum offset but they are double ended if you have a method to read from the maximum offset and write to the minimum offset.