Suppress deprecation warning from setuptools import.

Cython/Distutils/build_ext.py

@@ -7,6 +7,7 @@ building Cython extension modules."""
 
 __revision__ = "$Id:$"
 
+import inspect
 import sys
 import os
 from distutils.errors import DistutilsPlatformError
@@ -16,7 +17,12 @@ from distutils.command import build_ext as _build_ext
 from distutils import sysconfig
 import warnings
 
-warnings.warn(
+try:
+    from_setuptools = 'setuptools/extension.py' in inspect.getouterframes(inspect.currentframe(), 2)[2][1]
+except Exception:
+    from_setuptools = False
+if not from_setuptools:
+    warnings.warn(
         "Cython.Distutils.build_ext does not properly handle dependencies "
         "and is deprectated. Use Cython.Build.build_ext instead.")
 

setup.py

@@ -12,9 +12,6 @@ import sys
 import platform
 is_cpython = platform.python_implementation() == 'CPython'
 
-# Suppress warning.
-sys.modules[Extension.__module__].have_pyrex = lambda : True
-
 if sys.platform == "darwin":
     # Don't create resource files on OS X tar.
     os.environ['COPY_EXTENDED_ATTRIBUTES_DISABLE'] = 'true'