tools/python/pywrapper_template.txt

#!/bin/bash

# TODO(#7843): integration tests for failure to find python / wrong version
# found / error while trying to print version

set -euo pipefail

GENERAL_FAILURE_MESSAGE="Error: The default python toolchain \
(@bazel_tools//tools/python:autodetecting_toolchain) was unable to locate a \
suitable Python interpreter on the target platform at execution time. Please \
register an appropriate Python toolchain. See the documentation for \
py_runtime_pair here:
https://github.com/bazelbuild/bazel/blob/master/tools/python/toolchain.bzl."

# Try the "python%VERSION%" command name first, then fall back on "python".
PYTHON_BIN=$(which python%VERSION% || echo "")
USED_FALLBACK=0
if [[ -z "${PYTHON_BIN:-}" ]]; then
    PYTHON_BIN=$(which python || echo "")
    USED_FALLBACK=1
fi
if [[ -z "${PYTHON_BIN:-}" ]]; then
    echo "$GENERAL_FAILURE_MESSAGE"
    echo "Failure reason: Cannot locate 'python%VERSION%' or 'python' on the \
target platform's PATH, which is:
$PATH"
fi

# Verify that we grabbed an interpreter with the right version.
VERSION_STR=$("$PYTHON_BIN" -V 2>&1)
if ! grep -q " %VERSION%\." <<< $VERSION_STR; then
    echo "$GENERAL_FAILURE_MESSAGE"
    echo "Failure reason: According to '$PYTHON_BIN -V', version is \
'$VERSION_STR', but we need version %VERSION%"
fi

exec "$PYTHON_BIN" "$@"