Make the C extension optional.

setup.py

@@ -16,6 +16,7 @@
 
 import platform
 import sys
+import warnings
 
 try:
     # Use setuptools if available, for install_requires (among other things).
@@ -27,6 +28,89 @@ except ImportError:
 
 from distutils.core import Extension
 
+# The following code is copied from
+# https://github.com/mongodb/mongo-python-driver/blob/master/setup.py
+# to support installing without the extension on platforms where
+# no compiler is available.
+from distutils.command.build_ext import build_ext
+from distutils.errors import CCompilerError
+from distutils.errors import DistutilsPlatformError, DistutilsExecError
+if sys.platform == 'win32' and sys.version_info > (2, 6):
+    # 2.6's distutils.msvc9compiler can raise an IOError when failing to
+    # find the compiler
+    build_errors = (CCompilerError, DistutilsExecError,
+                    DistutilsPlatformError, IOError)
+else:
+    build_errors = (CCompilerError, DistutilsExecError, DistutilsPlatformError)
+
+class custom_build_ext(build_ext):
+    """Allow C extension building to fail.
+
+    The C extension speeds up websocket masking, but is not essential.
+    """
+
+    warning_message = """
+********************************************************************
+WARNING: %s could not
+be compiled. No C extensions are essential for Tornado to run,
+although they do result in significant speed improvements for
+websockets.
+%s
+
+Here are some hints for popular operating systems:
+
+If you are seeing this message on Linux you probably need to
+install GCC and/or the Python development package for your
+version of Python.
+
+Debian and Ubuntu users should issue the following command:
+
+    $ sudo apt-get install build-essential python-dev
+
+RedHat, CentOS, and Fedora users should issue the following command:
+
+    $ sudo yum install gcc python-devel
+
+If you are seeing this message on OSX please read the documentation
+here:
+
+http://api.mongodb.org/python/current/installation.html#osx
+********************************************************************
+"""
+
+    def run(self):
+        try:
+            build_ext.run(self)
+        except DistutilsPlatformError:
+            e = sys.exc_info()[1]
+            sys.stdout.write('%s\n' % str(e))
+            warnings.warn(self.warning_message % ("Extension modules",
+                                                  "There was an issue with "
+                                                  "your platform configuration"
+                                                  " - see above."))
+
+    def build_extension(self, ext):
+        name = ext.name
+        if sys.version_info[:3] >= (2, 4, 0):
+            try:
+                build_ext.build_extension(self, ext)
+            except build_errors:
+                e = sys.exc_info()[1]
+                sys.stdout.write('%s\n' % str(e))
+                warnings.warn(self.warning_message % ("The %s extension "
+                                                      "module" % (name,),
+                                                      "The output above "
+                                                      "this warning shows how "
+                                                      "the compilation "
+                                                      "failed."))
+        else:
+            warnings.warn(self.warning_message % ("The %s extension "
+                                                  "module" % (name,),
+                                                  "Please use Python >= 2.4 "
+                                                  "to take advantage of the "
+                                                  "extension."))
+
+
 kwargs = {}
 
 version = "3.2.dev2"
@@ -85,5 +169,6 @@ setuptools.setup(
         'Programming Language :: Python :: Implementation :: CPython',
         'Programming Language :: Python :: Implementation :: PyPy',
         ],
+    cmdclass={"build_ext": custom_build_ext},
     **kwargs
 )