queue: skip a source file that a landing moves or rewrites mid-scan instead of crashing next_functions

harbor/queue.py

@@ -47,8 +47,12 @@ class FunctionQueue:
             m = re.match(r"([0-9A-F]{6,8})_", path.name)
             if not m:
                 continue
-            with path.open(encoding="utf-8", errors="replace") as f:
-                head = [next(f, "") for _ in range(8)]
+            try:
+                with path.open(encoding="utf-8", errors="replace") as f:
+                    head = [next(f, "") for _ in range(8)]
+            except (FileNotFoundError, PermissionError):
+                continue                    # a landing on main moved or rewrote it while we scanned; its new path is found
+
             status = "readable" if any(line.startswith(READABLE) for line in head) else \
                 next((line.split("status:", 1)[1].strip() for line in head if "status:" in line), "raw")
             out[int(m.group(1), 16)] = (status, path.name)