Use custom stream for Windows compatibility in tests.

Author: AndreasBackx

tests/test_utils.py

@@ -280,9 +280,10 @@ def test_echo_color_flag_atty_and_not_jupyter_kernel(
     styled_text = click.style(text, fg="red")
     assert styled_text == stylized_text
 
-    click.echo(styled_text, color=color)
+    stream = StringIO()
+    click.echo(styled_text, color=color, file=stream)
     out, err = capfd.readouterr()
-    assert out == expected
+    assert stream.getvalue() == expected
 
 
 @pytest.mark.parametrize(