TestCommand: Make more use of universal_newlines

To always have string output from subprocesses in Python 2/3

Author: userzimmermann

test/test_nodely_bin.py

@@ -136,7 +136,8 @@ def test_check_output(
             node_package_command_output_regex):
         command = Command(node_package_command)
         assert node_package_command_output_regex.match(
-            command.check_output(node_package_command_args))
+            command.check_output(
+                node_package_command_args, universal_newlines=True))
 
         out, err = capfd.readouterr()
         assert not out and not err
@@ -159,7 +160,7 @@ def test__call__(
             node_package_command_output_regex):
         command = Command(node_package_command)
         assert node_package_command_output_regex.match(
-            command(*node_package_command_args))
+            command(*node_package_command_args, universal_newlines=True))
 
         out, err = capfd.readouterr()
         assert not out and not err