Fix AttributeError in sync httpx instrumentation (#1423)

* Fix AttributeError in sync httpx instrumentation Closes 1422 * Link PR Co-authored-by: Colton Myers <colton.myers@gmail.com>

Author: HenrikOssipoff

CHANGELOG.asciidoc

@@ -18,16 +18,17 @@ endif::[]
 ===== Bug fixes
 ////
 
-//=== Unreleased
+=== Unreleased
 
 // Unreleased changes go here
 // When the next release happens, nest these changes under the "Python Agent version 6.x" heading
 //[float]
 //===== Features
 //
 //
-//[float]
-//===== Bug fixes
+[float]
+===== Bug fixes
+* fix AttributeError in sync instrumentation of httpx {pull}1423[1423]
 
 
 [[release-notes-6.x]]

elasticapm/instrumentation/packages/httpx/sync/httpcore.py

@@ -91,10 +91,6 @@ def mutate_unsampled_call_args(self, module, method, wrapped, instance, args, kw
  trace_parent = transaction.trace_parent.copy_from(
  span_id=transaction.id, trace_options=TracingOptions(recorded=False)
  )
- if "headers" in kwargs:
- headers = kwargs["headers"]
- if headers is None:
- headers = []
- kwargs["headers"] = headers
- self._set_disttracing_headers(headers, trace_parent, transaction)
+ headers = utils.get_request_data(args, kwargs)[2]
+ utils.set_disttracing_headers(headers, trace_parent, transaction)
  return args, kwargs