Fix SyntaxWarning invalid escape sequence in Python code (#3433)

test/logo.test.py

@@ -43,7 +43,7 @@ class TestLogoCommand(TestCase):
     def test_logo_command(self):
         """Check that there are colors. For coverage"""
         code, out, err = self.t("logo rc._forcecolor:on")
-        self.assertRegex(out, ".\[48;5;\d+m  .\[0m")
+        self.assertRegex(out, r".\[48;5;\d+m  .\[0m")
 
     def test_logo_command_no_color(self):
         """Check that it only works with color. For coverage"""