feat: add status_code property on http error handling

docs/start.md

@@ -99,7 +99,7 @@ Creating a request does not actually call the API. To execute the request and ge
 try:
     response = request.execute()
 except HttpError as e:
-    print('Error response status code : {0}, reason : {1}'.format(e.resp.status, e.error_details))
+    print('Error response status code : {0}, reason : {1}'.format(e.status_code, e.error_details))
 ```
 
 Alternatively, you can combine previous steps on a single line:

googleapiclient/errors.py

@@ -43,6 +43,12 @@ def __init__(self, resp, content, uri=None):
         self.content = content
         self.uri = uri
         self.error_details = ""
+        self._get_reason()
+
+    @property
+    def status_code(self):
+        """Return the HTTP status code from the response content."""
+        return self.resp.status
 
     def _get_reason(self):
         """Calculate the reason for the error from the response content."""

tests/test_errors.py

@@ -83,6 +83,8 @@ def test_json_body(self):
             reason="Failed",
         )
         error = HttpError(resp, content, uri="http://example.org")
+        self.assertEqual(error.error_details, "error details")
+        self.assertEqual(error.status_code, 400)
         self.assertEqual(
             str(error),
             '<HttpError 400 when requesting http://example.org returned "country is required". Details: "error details">',