chore: improves logs for warning

CHANGELOG.md

@@ -18,6 +18,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Propagators use the root context as default for `extract` and do not modify
   the context if extracting from carrier does not work.
   ([#1811](https://github.com/open-telemetry/opentelemetry-python/pull/1811))
+- Improve warning when failing to decode byte attribute
+  ([#1810](https://github.com/open-telemetry/opentelemetry-python/pull/1810))
 
 ### Removed
 - Moved `opentelemetry-instrumentation` to contrib repository.

opentelemetry-sdk/src/opentelemetry/sdk/trace/__init__.py

@@ -685,7 +685,10 @@ def set_attributes(
                     try:
                         value = value.decode()
                     except ValueError:
-                        logger.warning("Byte attribute could not be decoded.")
+                        logger.warning(
+                            "Byte attribute could not be decoded for key `%s`.",
+                            key,
+                        )
                         return
                 self._attributes[key] = value