Adding a "does not raise" test for displaying errors.

borgmatic/config/validate.py

@@ -59,7 +59,7 @@ def parse_configuration(config_filename, schema_filename):
     return parsed_result
 
 
-def display_validation_error(validation_error):  # pragma: no cover
+def display_validation_error(validation_error):
     '''
     Given a Validation_error, display its error messages to stderr.
     '''

borgmatic/tests/integration/config/test_validate.py

@@ -111,3 +111,10 @@ def test_parse_configuration_raises_for_validation_error():
 
     with pytest.raises(module.Validation_error):
         module.parse_configuration('config.yaml', 'schema.yaml')
+
+
+def test_display_validation_error_does_not_raise():
+    flexmock(sys.modules['builtins']).should_receive('print')
+    error = module.Validation_error('config.yaml', ('oops', 'uh oh'))
+
+    module.display_validation_error(error)