[Bug]: `gradlew clean` involves external transform generation and fails

[tvalentyn]

What happened?

Repro:

 gradlew :sdks:python:cleanPython
To honour the JVM settings for this build a single-use Daemon process will be forked. For more on this, please refer to https://docs.gradle.org/8.4/userguide/gradle_daemon.html#sec:disabling_the_daemon in the Gradle documentation.
Daemon will be stopped at the end of the build 
Configuration on demand is an incubating feature.

> Task :sdks:python:cleanPython FAILED
b''
Traceback (most recent call last):
  File "setup.py", line 260, in generate_external_transform_wrappers
    subprocess.run([
  File "/home/valentyn/.pyenv/versions/3.8.18/lib/python3.8/subprocess.py", line 516, in run
    raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '['/home/valentyn/projects/beam/beam2/beam/build/gradleenv/1922375555/bin/python', '/home/valentyn/projects/beam/beam2/beam/sdks/python/gen_xlang_wrappers.py', '--cleanup', '--transforms-config-source', '/home/valentyn/projects/beam/beam2/beam/sdks/standard_external_transforms.yaml']' returned non-zero exit status 1.

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "setup.py", line 300, in <module>
    generate_external_transform_wrappers()
  File "setup.py", line 269, in generate_external_transform_wrappers
    raise RuntimeError(
RuntimeError: ('Could not generate external transform wrappers due to error: %s', b'Traceback (most recent call last):\n  File "/home/valentyn/projects/beam/beam2/beam/sdks/python/gen_xlang_wrappers.py", line 35, in <module>\n    import yaml\nModuleNotFoundError: No module named \'yaml\'\n')

FAILURE: Build failed with an exception.

Issue Priority

Priority: 3 (minor)

Issue Components

• Component: Python SDK
• Component: Java SDK
• Component: Go SDK
• Component: Typescript SDK
• Component: IO connector
• Component: Beam YAML
• Component: Beam examples
• Component: Beam playground
• Component: Beam katas
• Component: Website
• Component: Spark Runner
• Component: Flink Runner
• Component: Samza Runner
• Component: Twister2 Runner
• Component: Hazelcast Jet Runner
• Component: Google Cloud Dataflow Runner

[tvalentyn]

see also:

beam/buildSrc/src/main/groovy/org/apache/beam/gradle/BeamModulePlugin.groovy

Line 3025 in 1a0591e

def cleanPython = project.tasks.register('cleanPython') {