* Add Deleted error and disable all bad browser rows
* Avoid error when opening the browse screen to a card with a missing note (dae)
* In cards mode, a missing note is NotFound, not Deleted (dae)
So we distinguish between referential integrity error, and explicit
deletion.
* Remove redundant try block
* Use submodule imports in aqt
* Use submodule imports in pylib
* More submodule imports in pylib
These required removing some direct imports to get rid of import cycles.
This adds Python 3.9 and 3.10 typing syntax to files that import
attributions from __future___. Python 3.9 should be able to cope with
the 3.10 syntax, but Python 3.8 will no longer work.
On Windows/Mac, install the latest Python 3.9 version from python.org.
There are currently no orjson wheels for Python 3.10 on Windows/Mac,
which will break the build unless you have Rust installed separately.
On Linux, modern distros should have Python 3.9 available already. If
you're on an older distro, you'll need to build Python from source first.
