PythonBuild: Implementation of pythonBuild step (#3483)

* Implementation of pythonBuild step

* minor update and refactoring

* minor update

* add integration test and test project to testdata dir

* remove generated build data dir

* Rewrite some logic. Minor fix in integration tests for python

* Add new input parameters to pythonBuild.yaml

* rewrite logic
remove some checks

* rollback

* resolve merge conflict in piper.go
Update logic in python build. Create bom now works fine

* remove duplicate line

* refactoring fix

* resolve comment. Remove install build and change build command. Change twine upload command

* add groovy wrapper for pythonBuild step

* Rewrite tests. Remove some cheks from pythonBuild.go

* add some test to pythonBuild_test.go

* Add some parameters and credentials to the pythonBuild.groovy

* fix issue in unit tests

* add pythonBuild to fieldRelatedWhitelist

* update integration test for pythonBuild

* add imports

* update integration tests and add a new one

* minor fix

* fix some issues in integration tests

* update integration tests. Make it works again

Co-authored-by: Anil Keshav <anil.keshav@sap.com>
Co-authored-by: Oliver Nocon <33484802+OliverNocon@users.noreply.github.com>

integration/testdata/TestPythonIntegration/python-project/setup.py

@@ -0,0 +1,19 @@
+import setuptools
+
+setuptools.setup(
+    name="example-pkg",
+    version="0.0.1",
+    author="Example Author",
+    author_email="author@example.com",
+    description="A small example package",
+    long_description="Long description for small example package",
+    long_description_content_type="text/markdown",
+    url="https://github.com/example/pypi/github",
+    packages=setuptools.find_packages(),
+    classifiers=[
+        "Programming Language :: Python :: 3",
+        "License :: OSI Approved :: MIT License",
+        "Operating System :: OS Independent",
+    ],
+    python_requires='>=3.6',
+)