Increasing Singlefile header size because some URLs may be very long.

modules/archive/lib.py

@@ -507,7 +507,7 @@ def is_singlefile_file(path: pathlib.Path) -> bool:
         return True
     with path.open('rt') as fh:
         # Lastly, try to read the header of this HTML file.
-        header = fh.read(500)
+        header = fh.read(1000)
         if SINGLEFILE_HEADER in header:
             return True
     return False

modules/archive/models.py

@@ -149,7 +149,7 @@ class Archive(Base, ModelHelper):
             raise ValueError('Cannot read singlefile data when this has no files')
 
         with path.open('rt') as fh:
-            head = fh.read(500)
+            head = fh.read(1000)
             if 'Page saved with SingleFile' not in head:
                 return
             try: