message: Fix setup.py, comma makes download_url a tuple
diff: @@ -104,7 +104,8 @@ setup(
  author_email='maximebeauchemin@gmail.com',
  url='https://github.com/apache/incubator-superset',
  download_url=(
  - 'https://github.com/apache/incubator-superset/tarball/' + version_string,
  + 'https://github.com'
  + '/apache/incubator-superset/tarball/' + version_string
  ),
  classifiers=[
  'Programming Language :: Python :: 2.7',
  