$ find . -name \*.pyc -delete
$ PYTHONDONTWRITEBYTECODE=1 make test

Three test failures, which all seem to be duplicates of:

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FAIL: test_timestamp_overflow (test.test_importlib.source.test_file_loader.Source_SimpleTest)
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Traceback (most recent call last):
  File "/home/rosuav/cpython/Lib/test/test_importlib/source/test_file_loader.py", line 215, in test_timestamp_overflow
    self.assertTrue(os.path.exists(compiled))
AssertionError: False is not true

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It goes looking for the .pyc cached file, does not find it, and fails. Test should probably be skipped if bytecode isn't being written.