Prevent template changing options (#20775)

* Prevent complex template validation changing input value

* Remove deprecation warnings

tests/helpers/test_config_validation.py

@@ -402,8 +402,7 @@ def test_template():
     schema = vol.Schema(cv.template)
 
     for value in (None, '{{ partial_print }', '{% if True %}Hello', ['test']):
-        with pytest.raises(vol.Invalid,
-                           message='{} not considered invalid'.format(value)):
+        with pytest.raises(vol.Invalid):
             schema(value)
 
     options = (
@@ -433,6 +432,15 @@ def test_template_complex():
     for value in options:
         schema(value)
 
+    # ensure the validator didn't mutate the input
+    assert options == (
+        1, 'Hello',
+        '{{ beer }}',
+        '{% if 1 == 1 %}Hello{% else %}World{% endif %}',
+        {'test': 1, 'test2': '{{ beer }}'},
+        ['{{ beer }}', 1]
+    )
+
 
 def test_time_zone():
     """Test time zone validation."""