Simplify _build_http_response_error_message implementation

Author: anthony-c-martin

src/azure-cli/azure/cli/command_modules/resource/_utils.py

@@ -91,9 +91,7 @@ def _build_http_response_error_message(http_error):
     if not isinstance(http_error, HttpResponseError):
         raise TypeError("http_error must be an instance of HttpResponseError")
 
-    error_txt = http_error.response.text()
-
-    error_info = json.loads(error_txt)['error']
+    error_info = http_error.response.json()['error']
     error_details = error_info.pop('details') if 'details' in error_info else []
     err_messages = [f'{json.dumps(error_info)}']