Fix SassMiddleware to work on eventlet.wsgi

Author: dahlia

docs/changes.rst

@@ -8,6 +8,8 @@ To be released.
 
 - Follow up the libsass upstream: :upcommit:`3.0.1` ---
   See the `release note`__ of Libsass.
+- Fixed a bug that :class:`~sassutils.wsgi.SassMiddleware` never closes
+  the socket on some WSGI servers e.g. ``eventlet.wsgi``.
 
 __ https://github.com/sass/libsass/releases/tag/3.0.1
 

sassutils/wsgi.py

@@ -90,15 +90,17 @@ def __call__(self, environ, start_response):
                         self.quote_css_string(str(e)).encode('utf-8'),
                         b'; color: maroon; background-color: white; }'
                     ]
-                out = start_response('200 OK', [('Content-Type', 'text/css')])
-                with open(os.path.join(package_dir, result), 'rb') as in_:
-                    while 1:
-                        chunk = in_.read(4096)
-                        if chunk:
-                            out(chunk)
-                        else:
-                            break
-                return ()
+
+                def read_file(path):
+                    with open(path, 'rb') as in_:
+                        while 1:
+                            chunk = in_.read(4096)
+                            if chunk:
+                                yield chunk
+                            else:
+                                break
+                start_response('200 OK', [('Content-Type', 'text/css')])
+                return read_file(os.path.join(package_dir, result))
         return self.app(environ, start_response)
 
     @staticmethod