Fix DeprecationWarning raised by urllib3 1.26.13 (opensearch-project#246)

* Fix DeprecationWarning raised by urllib3 1.26.13

urllib3 has started to emit a DeprecationWarning whenever
HTTPResponse.getheaders() is called since version 1.26.13.

This changes the one place where this is done to instead use
HTTPResponse.headers instead, which is the recommend way of retrieving
the headers going forwards.

Signed-off-by: Jeppe Fihl-Pearson <jeppe@memrise.com>

* Add CHANGELOG entry

Signed-off-by: Jeppe Fihl-Pearson <jeppe@memrise.com>

Signed-off-by: Jeppe Fihl-Pearson <jeppe@memrise.com>

Author: Tenzer

CHANGELOG.md

@@ -18,7 +18,7 @@ Inspired from [Keep a Changelog](https://keepachangelog.com/en/1.0.0/)
 ### Removed
 
 ### Fixed
-
+- Fixed DeprecationWarning emitted from urllib3 1.26.13+ ([#246](https://github.com/opensearch-project/opensearch-py/pull/246))
 ### Security
 
 

opensearchpy/connection/http_urllib3.py

@@ -273,7 +273,7 @@ def perform_request(
             method, full_url, url, orig_body, response.status, raw_data, duration
         )
 
-        return response.status, response.getheaders(), raw_data
+        return response.status, response.headers, raw_data
 
     def get_response_headers(self, response):
         return {header.lower(): value for header, value in response.headers.items()}