Correct Content-Length to be valid even for non-ascii content

Author: seratch

slack_bolt/oauth/internals.py

@@ -35,7 +35,7 @@ def _build_callback_success_response(  # type: ignore
             status=200,
             headers={
                 "Content-Type": "text/html; charset=utf-8",
-                "Content-Length": len(html),
+                "Content-Length": len(bytes(html, "utf-8")),
                 "Set-Cookie": self._state_utils.build_set_cookie_for_deletion(),
             },
             body=html,
@@ -59,7 +59,7 @@ def _build_callback_failure_response(  # type: ignore
             status=status,
             headers={
                 "Content-Type": "text/html; charset=utf-8",
-                "Content-Length": len(html),
+                "Content-Length": len(bytes(html, "utf-8")),
                 "Set-Cookie": self._state_utils.build_set_cookie_for_deletion(),
             },
             body=html,