setup: Check for setuptools version

setup does require setuptools version >= 20.5

Author: Marius Kriegerowski

setup.py

@@ -6,8 +6,14 @@
 
 from codecs import StreamReader, open
 
+import setuptools
 from setuptools import find_packages, setup
 
+from distutils.version import LooseVersion
+if LooseVersion(setuptools.__version__) < LooseVersion('20.5'):
+    import sys
+    sys.exit('First, you have to upgrade your setuptools.')
+
 ##
 # Load long description for PyPi.
 with open('README.rst', 'r', 'utf-8') as f: # type: StreamReader