_iter_gitignore_files: Catch PermissionError

Relates to #1268

src/serena/util/file_system.py

@@ -165,10 +165,14 @@ class GitignoreParser:
 
         def scan(abs_path: str | None) -> Iterator[str]:
             for entry in os.scandir(abs_path):
-                if entry.is_dir(follow_symlinks=follow_symlinks):
-                    queue.append(entry.path)
-                elif entry.is_file(follow_symlinks=follow_symlinks) and entry.name == ".gitignore":
-                    yield entry.path
+                try:
+                    if entry.is_dir(follow_symlinks=follow_symlinks):
+                        queue.append(entry.path)
+                    elif entry.is_file(follow_symlinks=follow_symlinks) and entry.name == ".gitignore":
+                        yield entry.path
+                except PermissionError as ex:
+                    log.debug(f"Skipping entry due to permission error: {entry.path}", exc_info=ex)
+                    continue
 
         while queue:
             next_abs_path = queue.pop(0)