Add encoding='locale' support for TextIOWrapper

Author: MegasKomnenos

Lib/test/test_fileinput.py

@@ -391,8 +391,6 @@ def test__getitem__(self):
             retval2 = fi[1]
             self.assertEqual(retval2, "line2\n")
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test__getitem___deprecation(self):
         t = self.writeTmp("line1\nline2\n")
         with self.assertWarnsRegex(DeprecationWarning,
@@ -914,8 +912,6 @@ def test_empty_string(self):
     def test_no_ext(self):
         self.do_test_use_builtin_open("abcd", 2)
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     @unittest.skipUnless(gzip, "Requires gzip and zlib")
     def test_gz_ext_fake(self):
         original_open = gzip.open

vm/src/stdlib/io.rs

@@ -2193,10 +2193,14 @@ mod _io {
             *data = None;
 
             let encoding = match args.encoding {
-                Some(enc) => enc,
-                None => {
-                    // TODO: try os.device_encoding(fileno) and then locale.getpreferredencoding()
-                    PyStr::from(crate::codecs::DEFAULT_ENCODING).into_ref(&vm.ctx)
+                None if vm.state.settings.utf8_mode > 0 => PyStr::from("utf-8").into_ref(&vm.ctx),
+                Some(enc) if enc.as_str() != "locale" => enc,
+                _ => {
+                    // None without utf8_mode or "locale" encoding
+                    vm.import("locale", None, 0)?
+                        .get_attr("getencoding", vm)?
+                        .call((), vm)?
+                        .try_into_value(vm)?
                 }
             };