Tests: added test for callable write() in Python.

test/python/write/wsgi.py

@@ -0,0 +1,5 @@
+def application(env, start_response):
+    write = start_response('200', [('Content-Length', '10')])
+    write(b'012')
+    write(b'345')
+    return b'6789'

test/test_python_application.py

@@ -238,5 +238,10 @@ class TestUnitPythonApplication(unit.TestUnitApplicationPython):
             r'\[error\].+the application returned not an iterable object'),
             'not iterable')
 
+    def test_python_application_write(self):
+        self.load('write')
+
+        self.assertEqual(self.get()['body'], '0123456789', 'write')
+
 if __name__ == '__main__':
     unittest.main()