Replacer: Remove dead code

Author: jayvdb

src/tox/config/__init__.py

@@ -1801,16 +1801,11 @@ def _replace_match(self, match):
         if not any(g.values()):
             return os.pathsep
 
+        sub_type = g["sub_type"]
+
         if sub_value == "posargs":
             return self.reader.getposargs(match.group("default_value"))
 
-        try:
-            sub_type = g["sub_type"]
-        except KeyError:
-            raise tox.exception.ConfigError(
-                "Malformed substitution; no substitution type provided",
-            )
-
         if not sub_type and not g["default_value"] and sub_value == "/":
             return os.sep
         if sub_type == "env":