Update python-pymongo to 3.8.0.
- Fixed a bug in retryable writes where a previous command's "txnNumber" field could be sent leading to incorrect results.
- Fixed a memory leak of a few bytes on some insert, update, or delete commands when running against MongoDB 3.6+.
- Authentication fails when SCRAM-SHA-1 is used to authenticate users with only MONGODB-CR credentials.
- A millisecond rounding problem when decoding datetimes in the pure Python BSON decoder on 32 bit systems and AWS lambda.
- Support for single replica set multi-document ACID transactions.
- Support for wire protocol compression