Detect assignment expressions before Python 3.8 #41230

Job	Run time
cargo fmt	18s
cargo build (release)	0s
mkdocs	2m 24s
Determine changes	12s
pre-commit	2m 45s
python package	1m 24s
cargo build (msrv)	1m 28s
benchmarks	2m 23s
cargo clippy	1m 55s
cargo fuzz build	2m 21s
cargo shear	23s
cargo test (linux)	1m 5s
cargo test (linux, release)	2m 2s
cargo test (wasm)	1m 38s
cargo test (windows)	2m 16s
formatter instabilities and black similarity	2m 22s
test scripts	1m 3s
ecosystem	0s
fuzz parser	0s
test ruff-lsp	0s
	25m 59s

Provide feedback