Python: Copy Python extractor to codeql repo

python/extractor/cli-integration-test/README.md

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+# Extractor Python CodeQL CLI integration tests
+
+To ensure that the two work together as intended, and as an easy way to set up realistic test-cases.
+
+
+### Adding a new test case
+
+Add a new folder, place a file called `test.sh` in it, which should start with the code below. The script should exit with failure code to fail the test.
+
+```bash
+#!/bin/bash
+
+set -Eeuo pipefail # see https://vaneyckt.io/posts/safer_bash_scripts_with_set_euxo_pipefail/
+
+set -x
+
+CODEQL=${CODEQL:-codeql}
+
+SCRIPTDIR="$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )"
+cd "$SCRIPTDIR"
+```