Fix ExtendedInfo error handling for non-list item

Conflicts:
        sushy/exceptions.py

Change-Id: I2d082762fcf59d7b9bc8adc7c5159520ac628043
(cherry picked from commit 7ec04224b4)
(cherry picked from commit dfe6b33fa6)

releasenotes/notes/fix-extended-info-error-handling-73fecb6bf5c852ff.yaml

@@ -0,0 +1,7 @@
+---
+fixes:
+  - |
+    Fixes ``AttributeError: 'str' object has no attribute 'get'`` during error
+    handling. This occurs when BMC does not return a list of messages inside
+    ``@Message.ExtendedInfo``, but a single item. This has been observed with
+    iDRAC.

sushy/exceptions.py

@@ -101,9 +101,9 @@ class HTTPError(SushyError):
             self.code = self.body.get('code', 'Base.1.0.GeneralError')
             self.detail = self.body.get('message')
             ext_info = self.body.get('@Message.ExtendedInfo', [{}])
-            index = self._get_most_severe_msg_index(ext_info)
-            self.detail = ext_info[index].get('Message', self.detail)
-            error = '%s: %s' % (self.code, self.detail or 'unknown error')
+            message = self._get_most_severe_msg(ext_info)
+            self.detail = message or self.detail
+            error = '%s: %s' % (self.code, self.detail or 'unknown error.')
 
         kwargs = {'method': method, 'url': url, 'code': self.status_code,
                   'error': error}
@@ -112,13 +112,14 @@ class HTTPError(SushyError):
         super(HTTPError, self).__init__(**kwargs)
 
     @staticmethod
-    def _get_most_severe_msg_index(extended_info):
+    def _get_most_severe_msg(extended_info):
+        if not isinstance(extended_info, list):
+            return extended_info.get('Message', None)
         if len(extended_info) > 0:
             for sev in ['Critical', 'Warning']:
                 for i, m in enumerate(extended_info):
                     if m.get('Severity') == sev:
-                        return i
-        return 0
+                        return m.get('Message')
 
 
 class BadRequestError(HTTPError):

sushy/tests/unit/json_samples/error_single_ext_info.json

@@ -0,0 +1,13 @@
+{
+    "error": {
+        "code": "Base.1.5.GeneralError",
+        "message": "A general error has occurred. See ExtendedInfo for more information.",
+        "@Message.ExtendedInfo": {
+            "@odata.type": "#Message.v1_0_0.Message",
+            "MessageId": "Base.1.5.GeneralError",
+            "Message": "A general error has occurred. See Resolution for information on how to resolve the error.",
+            "Resolution": "Redfish request contains unsupported media type. Correct the request body and resubmit.",
+            "Severity": "Warning"
+        }
+    }
+}

sushy/tests/unit/test_connector.py

@@ -255,6 +255,21 @@ class ConnectorOpTestCase(base.TestCase):
         self.assertIsNotNone(exc.body)
         self.assertIn('body submitted was malformed JSON', exc.detail)
 
+    def test_known_http_error_nonlist_ext_info(self):
+        self.request.return_value.status_code =\
+            http_client.UNSUPPORTED_MEDIA_TYPE
+        with open('sushy/tests/unit/json_samples/'
+                  'error_single_ext_info.json') as f:
+            self.request.return_value.json.return_value = json.load(f)
+
+        with self.assertRaisesRegex(exceptions.HTTPError,
+                                    'See Resolution for information') as cm:
+            self.conn._op('POST', 'http://foo.bar')
+        exc = cm.exception
+        self.assertEqual(http_client.UNSUPPORTED_MEDIA_TYPE, exc.status_code)
+        self.assertIsNotNone(exc.body)
+        self.assertIn('See Resolution for information', exc.detail)
+
     def test_not_found_error(self):
         self.request.return_value.status_code = http_client.NOT_FOUND
         self.request.return_value.json.side_effect = ValueError('no json')