handle null statuses. fixes open-telemetry#820

Author: gregbuehler

Diff for: opentelemetry-instrumentation/src/opentelemetry/instrumentation/utils.py

@@ -46,6 +46,8 @@ def http_status_to_status_code(
         status (int): HTTP status code
     """
     # See: https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/trace/semantic_conventions/http.md#status
+    if status is None:
+        return StatusCode.UNSET
     if status < 100:
         return StatusCode.ERROR
     if status <= 299:

Diff for: opentelemetry-instrumentation/tests/test_utils.py

@@ -56,6 +56,14 @@ def test_http_status_to_status_code(self):
                 actual = http_status_to_status_code(int(status_code))
                 self.assertEqual(actual, expected, status_code)
 
+    def test_http_status_to_status_code_none(self):
+        for status_code, expected in (
+            (None, StatusCode.UNSET),
+        ):
+            with self.subTest(status_code=status_code):
+                actual = http_status_to_status_code(status_code)
+                self.assertEqual(actual, expected, status_code)
+
     def test_http_status_to_status_code_redirect(self):
         for status_code, expected in (
             (HTTPStatus.MULTIPLE_CHOICES, StatusCode.ERROR),