Add "py" as lang in conversable agent (#1062) (#2144)

* Add "py" as lang in conversable agent (#1062)

* Add conditions to allow for python executable variants (#1062)

* reverted import (#1062)

* Parameterized tests, moved Python variants to a constant (#1062)

* Moved Python variants to a constant (#1062)

* Update autogen/code_utils.py (#1062)

Co-authored-by: Eric Zhu <ekzhu@users.noreply.github.com>

* Update autogen/coding/local_commandline_code_executor.py (#1062)

Co-authored-by: Eric Zhu <ekzhu@users.noreply.github.com>

* Added PYTHON_VARIANTS as imported constant (#1062)

* ran pre-commit-check  (#1062)

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Co-authored-by: Chi Wang <wang.chi@microsoft.com>
Co-authored-by: Eric Zhu <ekzhu@users.noreply.github.com>