raise an exception if we find a cached file we can't validate

Author: keflavich

astroquery/query.py

@@ -489,9 +489,7 @@ def _download_file(self, url, local_filepath, timeout=None, auth=None,
             else:
                 # This case doesn't appear reachable under normal circumstances
                 # It is not covered by tests, and probably indicates a badly-behaved server
-                log.info(f"Found cached file {local_filepath}.  Could not verify length.")
-                response.close()
-                return local_filepath
+                raise ValueError(f"Found cached file {local_filepath}.  Could not verify length.")
         else:
             open_mode = 'wb'
             if head_safe: