resolve go-python#169 (comment)

Author: glaukiol1

os/os.module.go

@@ -136,22 +136,18 @@ func putenv(self py.Object, args py.Tuple) (py.Object, error) {
 
 // Unset (delete) the environment variable named key.
 func unsetenv(self py.Object, args py.Tuple) (py.Object, error) {
-	if len(args) == 1 && objectIsString(args[0]) {
-		_k, err := py.ReprAsString(args[0])
-		if err != nil {
-			return nil, py.ExceptionNewf(py.TypeError, "Unable to parse string") // this will never execute
-		}
-		key := strings.ReplaceAll(_k, "'", "") // required
-		err = os.Unsetenv(key)
-		if err != nil {
-			return nil, py.ExceptionNewf(py.OSError, "Unable to unset enviroment variable")
-		}
-		return py.None, nil
-	}
-	if len(args) == 0 {
+	if len(args) != 1 {
 		return nil, py.ExceptionNewf(py.TypeError, "missing one required argument: 'key:str'")
 	}
-	return nil, py.ExceptionNewf(py.TypeError, "str expected, not "+args[0].Type().Name)
+	k, ok := args[0].(py.String)
+	if !ok {
+		return nil, py.ExceptionNewf(py.TypeError, "str expected (pos 1), not "+args[0].Type().Name)
+	}
+	err := os.Unsetenv(string(k))
+	if err != nil {
+		return nil, py.ExceptionNewf(py.OSError, "Unable to unset enviroment variable")
+	}
+	return py.None, nil
 }
 
 // os._exit() immediate program termination; unlike sys.exit(), which raises a SystemExit, this function will termninate the program immediately.