Use always empty for None schema url value (#2764)

* Use always None for empty schema url value

Fixes #2750

* Revert "Use always None for empty schema url value"

This reverts commit 8ef29db.

* Use empty string as default value for schema_url

opentelemetry-sdk/src/opentelemetry/sdk/util/instrumentation.py

@@ -35,6 +35,8 @@ def __init__(
     ):
         self._name = name
         self._version = version
+        if schema_url is None:
+            schema_url = ""
         self._schema_url = schema_url
 
     def __repr__(self):
@@ -90,6 +92,8 @@ def __init__(
     ) -> None:
         self._name = name
         self._version = version
+        if schema_url is None:
+            schema_url = ""
         self._schema_url = schema_url
 
     def __repr__(self) -> str:

opentelemetry-sdk/tests/trace/test_trace.py

@@ -271,7 +271,7 @@ def test_invalid_instrumentation_info(self):
         )
         span1 = tracer1.start_span("foo")
         self.assertTrue(span1.is_recording())
-        self.assertEqual(tracer1.instrumentation_info.schema_url, None)
+        self.assertEqual(tracer1.instrumentation_info.schema_url, "")
         self.assertEqual(tracer1.instrumentation_info.version, "")
         self.assertEqual(tracer1.instrumentation_info.name, "")
 
@@ -280,7 +280,7 @@ def test_invalid_instrumentation_info(self):
         )
         span2 = tracer2.start_span("bar")
         self.assertTrue(span2.is_recording())
-        self.assertEqual(tracer2.instrumentation_info.schema_url, None)
+        self.assertEqual(tracer2.instrumentation_info.schema_url, "")
         self.assertEqual(tracer2.instrumentation_info.version, "")
         self.assertEqual(tracer2.instrumentation_info.name, "")