[MapProxy] Possible Bug in Cleanup?!

[Johannes Weskamm]

Hi,

I got a problem on a mapproxy-cleanup on an existing cache. It tries to 
delete non existing tiles, and hangs when it cant find these tiles.
I have a complete cache and do a cleanup based on polygons from a 
database (i think this doesnt matter).
After a while, i get this error (already reproduced this a few times):

.......
File 
"/opt/mapproxy/lib/python2.7/site-packages/mapproxy/seed/seeder.py", 
line 178, in _walk
     all_subtiles=all_subtiles, progress=progress)
   File 
"/opt/mapproxy/lib/python2.7/site-packages/mapproxy/seed/seeder.py", 
line 178, in _walk
     all_subtiles=all_subtiles, progress=progress)
   File 
"/opt/mapproxy/lib/python2.7/site-packages/mapproxy/seed/seeder.py", 
line 178, in _walk
     all_subtiles=all_subtiles, progress=progress)
   File 
"/opt/mapproxy/lib/python2.7/site-packages/mapproxy/seed/seeder.py", 
line 178, in _walk
     all_subtiles=all_subtiles, progress=progress)
   File 
"/opt/mapproxy/lib/python2.7/site-packages/mapproxy/seed/seeder.py", 
line 193, in _walk
     self.tile_mgr.is_stale(t)]
   File 
"/opt/mapproxy/lib/python2.7/site-packages/mapproxy/cache/tile.py", line 
170, in is_stale
     if not self.is_cached(tile):
   File 
"/opt/mapproxy/lib/python2.7/site-packages/mapproxy/cache/tile.py", line 
156, in is_cached
     self.cache.load_tile_metadata(tile)
   File 
"/opt/mapproxy/lib/python2.7/site-packages/mapproxy/cache/file.py", line 
138, in load_tile_metadata
     stats = os.lstat(location)
OSError: [Errno 2] No such file or directory: 
'/var/mapproxycache/osm_cache_EPSG900913/20/000/035/175/000/044/054.png'

The process hangs and i stop it with CTRL+C.
Trying it again seems to work most of the time without errors, what 
confuses me.
Wouldnt it be better if mapproxy keeps on cleaning, even if tiles havent 
been found?
The version i use is 1.2.1

Thanks,
Johannes