Add log_json=True test for log_request

Basic test just to make sure log_request handles log_json=True
properly.

notebook/tests/test_log.py

@@ -0,0 +1,40 @@
+import unittest
+from unittest import mock
+
+from notebook import log
+
+
+class TestLogRequest(unittest.TestCase):
+
+    @mock.patch('notebook.log.prometheus_log_method')
+    def test_log_request_json(self, mock_prometheus):
+        headers = {'Referer': 'test'}
+        request = mock.Mock(
+            request_time=mock.Mock(return_value=1),
+            headers=headers,
+            method='GET',
+            remote_ip='1.2.3.4',
+            uri='/notebooks/foo/bar'
+        )
+        handler = mock.MagicMock(
+            request=request,
+            get_status=mock.Mock(return_value=500)
+        )
+        logger = mock.MagicMock()
+        log.log_request(handler, log=logger, log_json=True)
+        # Since the status was 500 there should be two calls to log.error,
+        # one with the request headers and another with the other request
+        # parameters.
+        self.assertEqual(2, logger.error.call_count)
+        logger.error.assert_has_calls([
+            mock.call("", extra=dict(props=dict(headers))),
+            mock.call("", extra=dict(props={
+                'status': handler.get_status(),
+                'method': request.method,
+                'ip': request.remote_ip,
+                'uri': request.uri,
+                'request_time': 1000.0,
+                'referer': headers['Referer']
+            }))
+        ])
+        mock_prometheus.assert_called_once_with(handler)