message: Add Python 3.8 to classifiers and remove old ones
  According to
  nightly and TF 2.2 support Python 3.8.
diff: @@ -295,13 +295,12 @@ setup(
  'Intended Audience :: Education',
  'Intended Audience :: Science/Research',
  'License :: OSI Approved :: Apache Software License',
  - 'Programming Language :: Python :: 2',
  - 'Programming Language :: Python :: 2.7',
  'Programming Language :: Python :: 3',
  - 'Programming Language :: Python :: 3.4',
  'Programming Language :: Python :: 3.5',
  'Programming Language :: Python :: 3.6',
  'Programming Language :: Python :: 3.7',
  + 'Programming Language :: Python :: 3.8',
  + 'Programming Language :: Python :: 3 :: Only',
  'Topic :: Scientific/Engineering',
  'Topic :: Scientific/Engineering :: Mathematics',
  'Topic :: Scientific/Engineering :: Artificial Intelligence',
  