Print a warning in setup.py if basic dependencies aren't present

setup.py

@@ -9,10 +9,17 @@
 # So we don't really know if this is using the old setuptools or the
 # Distribute-provided version of setuptools.
 
-from setuptools import setup, find_packages
-from distutils.extension import Extension
+import traceback
+import sys
 
-from Cython.Build import cythonize
+try:
+    from setuptools import setup, find_packages
+    from distutils.extension import Extension
+    from Cython.Build import cythonize
+except ImportError:
+    traceback.print_exc()
+    print "Please install the prerequisites listed in README.txt"
+    sys.exit(1)
 
 # Hack to workaround logging/multiprocessing issue:
 # https://groups.google.com/d/msg/nose-users/fnJ-kAUbYHQ/_UsLN786ygcJ