remove backwards compat re-export of ConfigurationError from _loader.py

Import directly from _exceptions.py since this is new code with no existing
dependents on the _loader module path.

Assisted-by: Claude Sonnet 4.6

Author: MikeGoldsmith

opentelemetry-sdk/src/opentelemetry/sdk/_configuration/file/__init__.py

@@ -24,6 +24,7 @@
     '1.0'
 """
 
+from opentelemetry.sdk._configuration._exceptions import ConfigurationError
 from opentelemetry.sdk._configuration._propagator import (
     configure_propagator,
     create_propagator,
@@ -33,10 +34,7 @@
     EnvSubstitutionError,
     substitute_env_vars,
 )
-from opentelemetry.sdk._configuration.file._loader import (
-    ConfigurationError,
-    load_config_file,
-)
+from opentelemetry.sdk._configuration.file._loader import load_config_file
 
 __all__ = [
     "load_config_file",

opentelemetry-sdk/src/opentelemetry/sdk/_configuration/file/_loader.py

@@ -60,10 +60,6 @@ def _get_schema() -> dict:
 _logger = logging.getLogger(__name__)
 
 
-# Re-export for backwards compatibility
-__all__ = ["ConfigurationError", "load_config_file"]
-
-
 def load_config_file(file_path: str) -> OpenTelemetryConfiguration:
     """Load and parse an OpenTelemetry configuration file.
 

opentelemetry-sdk/tests/_configuration/test_propagator.py

@@ -22,11 +22,11 @@
 from opentelemetry.baggage.propagation import W3CBaggagePropagator
 from opentelemetry.environment_variables import OTEL_PROPAGATORS
 from opentelemetry.propagators.composite import CompositePropagator
+from opentelemetry.sdk._configuration._exceptions import ConfigurationError
 from opentelemetry.sdk._configuration._propagator import (
     configure_propagator,
     create_propagator,
 )
-from opentelemetry.sdk._configuration.file._loader import ConfigurationError
 from opentelemetry.sdk._configuration.models import (
     Propagator as PropagatorConfig,
 )
@@ -273,5 +273,6 @@ def test_otel_propagators_env_var_ignored(self):
             propagator = mock_set.call_args[0][0]
             self.assertEqual(len(propagator._propagators), 1)  # type: ignore[attr-defined]
             self.assertIsInstance(
-                propagator._propagators[0], TraceContextTextMapPropagator  # type: ignore[attr-defined]
+                propagator._propagators[0],
+                TraceContextTextMapPropagator,  # type: ignore[attr-defined]
             )