[python] removed deprecated code (#2474)

python-package/lightgbm/__init__.py

@@ -11,8 +11,6 @@ from .callback import (early_stopping, print_evaluation, record_evaluation,
 from .engine import cv, train
 
 import os
-import warnings
-from platform import system
 
 try:
     from .sklearn import LGBMModel, LGBMRegressor, LGBMClassifier, LGBMRanker
@@ -36,13 +34,3 @@ __all__ = ['Dataset', 'Booster',
            'LGBMModel', 'LGBMRegressor', 'LGBMClassifier', 'LGBMRanker',
            'print_evaluation', 'record_evaluation', 'reset_parameter', 'early_stopping',
            'plot_importance', 'plot_split_value_histogram', 'plot_metric', 'plot_tree', 'create_tree_digraph']
-
-# REMOVEME: remove warning after 2.3.0 version release
-if system() == 'Darwin':
-    warnings.warn("Starting from version 2.2.1, the library file in distribution wheels for macOS "
-                  "is built by the Apple Clang (Xcode_8.3.3) compiler.\n"
-                  "This means that in case of installing LightGBM from PyPI via the ``pip install lightgbm`` command, "
-                  "you don't need to install the gcc compiler anymore.\n"
-                  "Instead of that, you need to install the OpenMP library, "
-                  "which is required for running LightGBM on the system with the Apple Clang compiler.\n"
-                  "You can install the OpenMP library by the following command: ``brew install libomp``.", UserWarning)