MNT Simplify creation of pickle path (scikit-learn#15237)

Author: sbehren

sklearn/datasets/base.py

@@ -8,7 +8,6 @@
 # License: BSD 3 clause
 import os
 import csv
-import sys
 import shutil
 import warnings
 from collections import namedtuple
@@ -847,30 +846,18 @@ def load_sample_image(image_name):
 
 
 def _pkl_filepath(*args, **kwargs):
-    """Ensure different filenames for Python 2 and Python 3 pickles
+    """Return filename for Python 3 pickles
 
-    An object pickled under Python 3 cannot be loaded under Python 2. An object
-    pickled under Python 2 can sometimes not be loaded correctly under Python 3
-    because some Python 2 strings are decoded as Python 3 strings which can be
-    problematic for objects that use Python 2 strings as byte buffers for
-    numerical data instead of "real" strings.
+    args[-1] is expected to be the ".pkl" filename. For compatibility with
+    older scikit-learn versions, a suffix is inserted before the extension.
 
-    Therefore, dataset loaders in scikit-learn use different files for pickles
-    manages by Python 2 and Python 3 in the same SCIKIT_LEARN_DATA folder so as
-    to avoid conflicts.
-
-    args[-1] is expected to be the ".pkl" filename. Under Python 3, a suffix is
-    inserted before the extension to s
-
-    _pkl_filepath('/path/to/folder', 'filename.pkl') returns:
-      - /path/to/folder/filename.pkl under Python 2
-      - /path/to/folder/filename_py3.pkl under Python 3+
+    _pkl_filepath('/path/to/folder', 'filename.pkl') returns
+    '/path/to/folder/filename_py3.pkl'
 
     """
     py3_suffix = kwargs.get("py3_suffix", "_py3")
     basename, ext = splitext(args[-1])
-    if sys.version_info[0] >= 3:
-        basename += py3_suffix
+    basename += py3_suffix
     new_args = args[:-1] + (basename + ext,)
     return join(*new_args)