Fix Status-Line in HTTP response

There is a strict rule about constructing status line for HTTP:
'...Status-Line, consisting of the protocol version followed by a
numeric status code and its associated textual phrase, with each
element separated by SP characters'
(http://www.faqs.org/rfcs/rfc2616.html)

This patch ensures an associated textual phrase for a status code
is always written in the HTTP response.

Closes-Bug: #1496055
Change-Id: I68d4c41d0c04871eb032d23d7b16aa2bf2c0bb73

nova/exception.py

@@ -30,6 +30,7 @@ from oslo_log import log as logging
 from oslo_utils import excutils
 import six
 import webob.exc
+from webob import util as woutil
 
 from nova.i18n import _, _LE
 from nova import safe_utils
@@ -47,9 +48,24 @@ CONF.register_opts(exc_log_opts)
 
 
 class ConvertedException(webob.exc.WSGIHTTPException):
-    def __init__(self, code=500, title="", explanation=""):
+    def __init__(self, code, title="", explanation=""):
         self.code = code
-        self.title = title
+        # There is a strict rule about constructing status line for HTTP:
+        # '...Status-Line, consisting of the protocol version followed by a
+        # numeric status code and its associated textual phrase, with each
+        # element separated by SP characters'
+        # (http://www.faqs.org/rfcs/rfc2616.html)
+        # 'code' and 'title' can not be empty because they correspond
+        # to numeric status code and its associated text
+        if title:
+            self.title = title
+        else:
+            try:
+                self.title = woutil.status_reasons[self.code]
+            except KeyError:
+                msg = _LE("Improper or unknown HTTP status code used: %d")
+                LOG.error(msg, code)
+                self.title = woutil.status_generic_reasons[self.code // 100]
         self.explanation = explanation
         super(ConvertedException, self).__init__()
 

nova/tests/unit/test_exception.py

@@ -17,6 +17,7 @@
 import inspect
 
 import six
+from webob.util import status_reasons
 
 from nova import context
 from nova import exception
@@ -146,10 +147,29 @@ class NovaExceptionTestCase(test.NoDBTestCase):
         self.assertEqual("some message %(somearg)s", exc.format_message())
 
 
+class ConvertedExceptionTestCase(test.NoDBTestCase):
+    def test_instantiate(self):
+        exc = exception.ConvertedException(400, 'Bad Request', 'reason')
+        self.assertEqual(exc.code, 400)
+        self.assertEqual(exc.title, 'Bad Request')
+        self.assertEqual(exc.explanation, 'reason')
+
+    def test_instantiate_without_title_known_code(self):
+        exc = exception.ConvertedException(500)
+        self.assertEqual(exc.title, status_reasons[500])
+
+    def test_instantiate_without_title_unknown_code(self):
+        exc = exception.ConvertedException(499)
+        self.assertEqual(exc.title, 'Unknown Client Error')
+
+    def test_instantiate_bad_code(self):
+        self.assertRaises(KeyError, exception.ConvertedException, 10)
+
+
 class ExceptionTestCase(test.NoDBTestCase):
     @staticmethod
     def _raise_exc(exc):
-        raise exc()
+        raise exc(500)
 
     def test_exceptions_raise(self):
         # NOTE(dprince): disable format errors since we are not passing kwargs