[Python] Migrate from yapf to black (#33138)

- Switched  from yapf to black
- Reconfigure isort for black
- Resolve black/pylint idiosyncrasies 

Note: I used `--experimental-string-processing` because black was
producing "implicit string concatenation", similar to what described
here: psf/black#1837. While currently this
feature is experimental, it will be enabled by default:
psf/black#2188. After running black with the
new string processing so that the generated code merges these `"hello" "
world"` strings concatenations, then I removed
`--experimental-string-processing` for stability, and regenerated the
code again.

To the reviewer: don't even try to open "Files Changed" tab 😄 It's
better to review commit-by-commit, and ignore `run black and isort`.

README.md

@@ -216,7 +216,7 @@ from your dev environment. You need:
 
 ### Making changes to the driver
 1. Install additional dev packages: `pip install -r requirements-dev.txt`
-2. Use `./bin/yapf.sh` and `./bin/isort.sh` helpers to auto-format code.
+2. Use `./bin/black.sh` and `./bin/isort.sh` helpers to auto-format code.
 
 ### Updating Python Dependencies
 

bin/yapf.sh → bin/black.sh

@@ -17,17 +17,19 @@ set -eo pipefail
 
 display_usage() {
   cat <<EOF >/dev/stderr
-A helper to run yapf formatter.
+A helper to run black formatter.
 
 USAGE: $0 [--diff]
    --diff: Do not apply changes, only show the diff
+   --check: Do not apply changes, only print what files will be changed
 
 ENVIRONMENT:
    XDS_K8S_DRIVER_VENV_DIR: the path to python virtual environment directory
                             Default: $XDS_K8S_DRIVER_DIR/venv
 EXAMPLES:
 $0
 $0 --diff
+$0 --check
 EOF
   exit 1
 }
@@ -48,11 +50,11 @@ source "${XDS_K8S_DRIVER_DIR}/bin/ensure_venv.sh"
 
 if [[ "$1" == "--diff" ]]; then
   readonly MODE="--diff"
+elif [[ "$1" == "--check" ]]; then
+  readonly MODE="--check"
 else
-  readonly MODE="--in-place"
-  readonly VERBOSE="--verbose" # print out file names while processing
+  readonly MODE=""
 fi
 
-exec python -m yapf "${MODE}" ${VERBOSE:-} \
-  --parallel --recursive --style=../../../setup.cfg \
-  framework bin tests
+# shellcheck disable=SC2086
+exec python -m black --config=../../../black.toml ${MODE} .