Bump copyright year

See merge request !11

Deliver messages to HyperKitty as bytes.

Closes #27

See merge request !12

mailman-hyperkitty.cfg: clarification for api_key

See merge request !13

* log an explicit error when archiving failed and email is requeued
* avoid encoding errors filling the logs with stack traces
* log an explicit error when message to text conversion failed
* log an explicit error when archiving message failed

* Remove useless exception handling addition from previous commit.
* Add message information when HyperKitty fails.

Also flake8 fixes.

Also, remove a stray import.

Fixes #26

Remove runtime dependency on setuptools.

Closes #26

See merge request !15

This should avoid un-handled exceptions thrown by requests due to errors
related to talking to Hyperkitty.

Fixes #4, #20

Handle exceptions that can be raised by trying to fetch URLs.

Closes #20 and #4

See merge request !16

chore: Bump release version, and add support for Python 3.10.

See merge request !17

README.rst: typo

See merge request !18

Since Python 3.3 the unittest module has mock support which completely
replaces the seperate mock module.

Use Python's unittest.mock

See merge request !19

Add support for Python 3.11 and drop 3.6

See merge request !20