Merge branch 'add-os-module' of https://github.com/glaukiol1/gpython into add-os-module

Author: glaukiol1

os/os.module.go

@@ -79,7 +79,9 @@ func chdir(self py.Object, args py.Tuple) (py.Object, error) {
 	if len(args) == 0 {
 		return nil, py.ExceptionNewf(py.TypeError, "Missing required argument 'path' (pos 1)")
 	}
-	if objectIsString(args[0]) {
+	if !objectIsString(args[0]) {
+	    return nil, py.ExceptionNewf(py.TypeError, "str expected, not "+args[0].Type().Name)
+	}
 		dir, err := py.ReprAsString(args[0])
 		if err != nil {
 			return nil, py.ExceptionNewf(py.TypeError, "Failed to parse string") // never going to run