Tests: added Python test with iterator context.

test/python/ctx_iter_atexit/wsgi.py

@@ -0,0 +1,23 @@
+import atexit
+
+class application:
+    def __init__(self, environ, start_response):
+        self.environ = environ
+        self.start = start_response
+
+    def __iter__(self):
+        atexit.register(self._atexit)
+
+        content_length = int(self.environ.get('CONTENT_LENGTH', 0))
+        body = bytes(self.environ['wsgi.input'].read(content_length))
+
+        self.start('200', [
+            ('Content-Type', self.environ.get('CONTENT_TYPE')),
+            ('Content-Length', str(len(body)))
+        ])
+        yield body
+
+    def _atexit(self):
+        self.start('200', [
+            ('Content-Length', '0')
+        ])