Use native string for disttracing header (#390)

* Use native strings for headers

* Remove redundant str

* Align to_str with from_string

* Black

Author: hannseman

elasticapm/instrumentation/packages/urllib3.py

@@ -56,7 +56,7 @@ def call(self, module, method, wrapped, instance, args, kwargs):
                 trace_parent = transaction.trace_parent.copy_from(
                     span_id=parent_id, trace_options=TracingOptions(recorded=True)
                 )
-                headers[constants.TRACEPARENT_HEADER_NAME] = trace_parent.to_ascii()
+                headers[constants.TRACEPARENT_HEADER_NAME] = trace_parent.to_string()
             return wrapped(*args, **kwargs)
 
     def mutate_unsampled_call_args(self, module, method, wrapped, instance, args, kwargs, transaction):
@@ -69,5 +69,5 @@ def mutate_unsampled_call_args(self, module, method, wrapped, instance, args, kw
             if headers is None:
                 headers = {}
                 kwargs["headers"] = headers
-            headers[constants.TRACEPARENT_HEADER_NAME] = trace_parent.to_ascii()
+            headers[constants.TRACEPARENT_HEADER_NAME] = trace_parent.to_string()
         return args, kwargs

elasticapm/utils/disttracing.py

@@ -22,7 +22,7 @@ def copy_from(self, version=None, trace_id=None, span_id=None, trace_options=Non
         )
 
     def to_string(self):
-        return u"{:02x}-{}-{}-{:02x}".format(self.version, self.trace_id, self.span_id, self.trace_options.asByte)
+        return "{:02x}-{}-{}-{:02x}".format(self.version, self.trace_id, self.span_id, self.trace_options.asByte)
 
     def to_ascii(self):
         return self.to_string().encode("ascii")

tests/utils/test_disttracing_header.py

@@ -1,6 +1,5 @@
 import pytest
 
-from elasticapm.utils import compat
 from elasticapm.utils.disttracing import TraceParent
 
 
@@ -14,15 +13,15 @@ def test_tracing_options(tracing_bits, expected):
 def test_unknown_header_components_ignored():
     header = "01-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-03-xyz"
     trace_parent = TraceParent.from_string(header)
-    assert trace_parent.to_ascii().decode("ascii") == "01-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-03"
+    assert trace_parent.to_string() == "01-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-03"
 
 
-def test_trace_parent_to_ascii():
+def test_trace_parent_to_str():
     header = "00-0af7651916cd43dd8448eb211c80319c-b7ad6b7169203331-03"
     trace_parent = TraceParent.from_string(header)
-    result = trace_parent.to_ascii()
-    assert isinstance(result, compat.binary_type)
-    assert header.encode("ascii") == result
+    result = trace_parent.to_string()
+    assert isinstance(result, str)
+    assert header == result
 
 
 def test_trace_parent_wrong_version(caplog):