stdlib/io.rs: align negative-fd-from-opener exception with CPython

Lib/test/test_io.py

@@ -864,8 +864,6 @@ class IOTest(unittest.TestCase):
         with self.open("non-existent", "r", opener=opener) as f:
             self.assertEqual(f.read(), "egg\n")
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_bad_opener_negative_1(self):
         # Issue #27066.
         def badopener(fname, flags):
@@ -874,8 +872,6 @@ class IOTest(unittest.TestCase):
             open('non-existent', 'r', opener=badopener)
         self.assertEqual(str(cm.exception), 'opener returned -1')
 
-    # TODO: RUSTPYTHON
-    @unittest.expectedFailure
     def test_bad_opener_other_negative(self):
         # Issue #27066.
         def badopener(fname, flags):

vm/src/stdlib/io.rs

@@ -3857,7 +3857,7 @@ mod fileio {
                 }
                 let fd = i32::try_from_object(vm, fd)?;
                 if fd < 0 {
-                    return Err(vm.new_os_error("Negative file descriptor".to_owned()));
+                    return Err(vm.new_value_error(format!("opener returned {}", fd)));
                 }
                 fd
             } else if let Some(i) = name.payload::<crate::builtins::PyInt>() {