rust-cpython: do not convert warning pattern to utf-8 bytes

On Unix, both Rust Path and Mercurial expect a locale-dependent bytes,
and we don't support Windows yet.

rust/hg-core/src/utils/files.rs

@@ -29,6 +29,14 b' pub fn get_path_from_bytes(bytes: &[u8])'
     Path::new(os_str)
 }
 
+// TODO: need to convert from WTF8 to MBCS bytes on Windows.
+// that's why Vec<u8> is returned.
+#[cfg(unix)]
+pub fn get_bytes_from_path(path: impl AsRef<Path>) -> Vec<u8> {
+    use std::os::unix::ffi::OsStrExt;
+    path.as_ref().as_os_str().as_bytes().to_vec()
+}
+
 /// An iterator over repository path yielding itself and its ancestors.
 #[derive(Copy, Clone, Debug)]
 pub struct Ancestors<'a> {

rust/hg-cpython/src/filepatterns.rs

@@ -68,7 +68,7 b' fn warnings_to_py_bytes('
         .iter()
         .map(|(path, syn)| {
             (
-                PyBytes::new(py, &path.to_string_lossy().as_bytes()),
+                PyBytes::new(py, &files::get_bytes_from_path(path)),
                 PyBytes::new(py, syn),
             )
         })