Basic test for setting signing_metadata_url_base

Check that this config option actually gets loaded; rename previous test
to avoid name collision and better describe what it does.

tests/base/test_context.py

@@ -97,6 +97,14 @@ def test_old_channel_alias(self):
         ]
 
     def test_signing_metadata_url_base(self):
+        SIGNING_URL_BASE = "https://conda.example.com/pkgs"
+        string = f"signing_metadata_url_base: {SIGNING_URL_BASE}"
+        reset_context()
+        rd = odict(testdata=YamlRawParameter.make_raw_parameters('testdata', yaml_round_trip_load(string)))
+        context._set_raw_data(rd)
+        assert context.signing_metadata_url_base == SIGNING_URL_BASE
+
+    def test_signing_metadata_url_base_empty_default_channels(self):
         string = dals("""
         default_channels: []
         """)