Add str.__rmod__() method. #190 (#1262)

* Add str.__rmod__ method.

* Add tests for str.__rmod__ method.

* Improve test for str.__rmod__ method.

* Change str.__rmod__ method return value type.

* Format with rustfmt.

* Remove not required code of str.__rmod__ method.

* Improve with clippy.

tests/snippets/strings.py

@@ -293,3 +293,6 @@ assert next(str_iter_reversed) == "2"
 assert next(str_iter_reversed) == "1"
 assert next(str_iter_reversed, None) == None
 assert_raises(StopIteration, lambda: next(str_iter_reversed))
+
+assert str.__rmod__('%i', 30) == NotImplemented
+assert_raises(TypeError, lambda: str.__rmod__(30, '%i'))

vm/src/obj/objstr.rs

@@ -518,6 +518,11 @@ impl PyString {
         do_cformat(vm, format_string, values.clone())
     }
 
+    #[pymethod(name = "__rmod__")]
+    fn rmod(&self, _values: PyObjectRef, vm: &VirtualMachine) -> PyResult {
+        Ok(vm.ctx.not_implemented())
+    }
+
     #[pymethod]
     fn format(vm: &VirtualMachine, args: PyFuncArgs) -> PyResult {
         if args.args.is_empty() {