tests/test-check-py3-compat.t

rust-cpython: prepare for writing tests that require libpython

What I wanted is to disable the "cpython/extension-module<ver>" feature
while building tests executable, but that seems not doable. Instead,
this patch adds new features dedicated for tests.

The make rule is extracted so that we can easily run cargo tests.

Added a minimal test of ref-sharing as an example. More tests will follow.

#require test-repo

  $ . "$TESTDIR/helpers-testrepo.sh"
  $ cd "$TESTDIR"/..

#if no-py3
  $ testrepohg files 'set:(**.py)' \
  > -X contrib/automation/ \
  > -X contrib/grey.py \
  > -X contrib/packaging/hgpackaging/ \
  > -X contrib/packaging/inno/ \
  > -X contrib/packaging/wix/ \
  > -X hgdemandimport/demandimportpy2.py \
  > -X mercurial/thirdparty/cbor \
  > | sed 's|\\|/|g' | xargs "$PYTHON" contrib/check-py3-compat.py
  contrib/python-zstandard/setup.py not using absolute_import
  contrib/python-zstandard/setup_zstd.py not using absolute_import
  contrib/python-zstandard/tests/common.py not using absolute_import
  contrib/python-zstandard/tests/test_buffer_util.py not using absolute_import
  contrib/python-zstandard/tests/test_compressor.py not using absolute_import
  contrib/python-zstandard/tests/test_compressor_fuzzing.py not using absolute_import
  contrib/python-zstandard/tests/test_data_structures.py not using absolute_import
  contrib/python-zstandard/tests/test_data_structures_fuzzing.py not using absolute_import
  contrib/python-zstandard/tests/test_decompressor.py not using absolute_import
  contrib/python-zstandard/tests/test_decompressor_fuzzing.py not using absolute_import
  contrib/python-zstandard/tests/test_estimate_sizes.py not using absolute_import
  contrib/python-zstandard/tests/test_module_attributes.py not using absolute_import
  contrib/python-zstandard/tests/test_train_dictionary.py not using absolute_import
  setup.py not using absolute_import
#endif

#if py3
  $ testrepohg files 'set:(**.py) - grep(pygments)' \
  > -X hgdemandimport/demandimportpy2.py \
  > -X hgext/fsmonitor/pywatchman \
  > -X mercurial/cffi \
  > -X mercurial/thirdparty \
  > | sed 's|\\|/|g' | xargs "$PYTHON" contrib/check-py3-compat.py \
  > | sed 's/[0-9][0-9]*)$/*)/'
  hgext/convert/transport.py: error importing: <*Error> No module named 'svn.client' (error at transport.py:*) (glob) (?)
  hgext/infinitepush/sqlindexapi.py: error importing: <*Error> No module named 'mysql' (error at sqlindexapi.py:*) (glob) (?)
  mercurial/scmwindows.py: error importing: <ValueError> _type_ 'v' not supported (error at win32.py:*) (no-windows !)
  mercurial/win32.py: error importing: <ValueError> _type_ 'v' not supported (error at win32.py:*) (no-windows !)
  mercurial/windows.py: error importing: <ModuleNotFoundError> No module named 'msvcrt' (error at windows.py:*) (no-windows !)
  mercurial/posix.py: error importing: <ModuleNotFoundError> No module named 'fcntl' (error at posix.py:*) (windows !)
  mercurial/scmposix.py: error importing: <ModuleNotFoundError> No module named 'fcntl' (error at scmposix.py:*) (windows !)
#endif

#if py3 pygments
  $ testrepohg files 'set:(**.py) and grep(pygments)' | sed 's|\\|/|g' \
  > | xargs "$PYTHON" contrib/check-py3-compat.py \
  > | sed 's/[0-9][0-9]*)$/*)/'
#endif