Can we have an option to ignore errors when listing files for rsync?

Just having a broken symlink makes it stop. It would be nice if you could tell it to keep going and just ignore the file it couldn't list.

```
poizan@dy:~$ sudo gsutil/gsutil rsync -C -r /mnt/ext/PoiDisk/Backup/ gs://last-line-of-defence/Backup
Building synchronization state...
At source listing 10000...
At source listing 20000...
At source listing 30000...
Caught non-retryable exception while listing file:///mnt/ext/PoiDisk/Backup/: [Errno 2] No such file or directory: '/mnt/ext/PoiDisk/Backup/dybackup/poizanhome/poizan/.pftp'
At destination listing 10000...
At destination listing 20000...
At destination listing 30000...
CommandException: Caught non-retryable exception - aborting rsync
```