Use new_os_subtype_error for termios error construction

- Replace manual exception creation with new_os_subtype_error in termios
- Remove redundant .to_owned() calls in os.link() error messages

crates/stdlib/src/termios.rs

@@ -261,13 +261,12 @@ mod termios {
     }
 
     fn termios_error(err: std::io::Error, vm: &VirtualMachine) -> PyBaseExceptionRef {
-        vm.new_exception(
+        vm.new_os_subtype_error(
             error_type(vm),
-            vec![
-                err.posix_errno().to_pyobject(vm),
-                vm.ctx.new_str(err.to_string()).into(),
-            ],
+            Some(err.posix_errno()),
+            vm.ctx.new_str(err.to_string()),
         )
+        .upcast()
     }
 
     #[pyattr(name = "error", once)]

crates/vm/src/stdlib/os.rs

@@ -1278,9 +1278,9 @@ pub(super) mod _os {
         {
             use std::os::unix::ffi::OsStrExt;
             let src_cstr = std::ffi::CString::new(src.path.as_os_str().as_bytes())
-                .map_err(|_| vm.new_value_error("embedded null byte".to_owned()))?;
+                .map_err(|_| vm.new_value_error("embedded null byte"))?;
             let dst_cstr = std::ffi::CString::new(dst.path.as_os_str().as_bytes())
-                .map_err(|_| vm.new_value_error("embedded null byte".to_owned()))?;
+                .map_err(|_| vm.new_value_error("embedded null byte"))?;
 
             let flags = if follow_symlinks.0 {
                 libc::AT_SYMLINK_FOLLOW
@@ -1315,7 +1315,7 @@ pub(super) mod _os {
             // or raise NotImplementedError if explicitly set to False
             if !follow_symlinks.0 {
                 return Err(vm.new_not_implemented_error(
-                    "link: follow_symlinks unavailable on this platform".to_owned(),
+                    "link: follow_symlinks unavailable on this platform",
                 ));
             }