Handle `BucketNotEmpty` better

[Jc2k]

Traceback (most recent call last):
  File "/app/bin/tenops", line 9, in <module>
    load_entry_point('ten-self-service==2.16.4.dev0', 'console_scripts', 'tenops')()
  File "/app/src/ten_self_service/scripts/tenops.py", line 7, in main
    Console()()
  File "/app/src/ten_self_service/ops/console.py", line 231, in __call__
    return self.args.func(self.args)
  File "/app/local/lib/python2.7/site-packages/touchdown/core/main.py", line 55, in __call__
    return g.execute(*args, **kwargs)
  File "/app/local/lib/python2.7/site-packages/touchdown/goals/action.py", line 72, in execute
    self.apply_resources()
  File "/app/local/lib/python2.7/site-packages/touchdown/goals/action.py", line 57, in apply_resources
    for status in self.Map(self.ui, dep_map, self.apply_resource):
  File "/app/local/lib/python2.7/site-packages/touchdown/core/map.py", line 172, in __iter__
    raise caught_error
botocore.exceptions.ClientError: An error occurred (BucketNotEmpty) when calling the DeleteBucket operation: The bucket you tried to delete is not empty

This is typically an issue when dealing with e.g. cloudfront logs which continue to arrive even after a cloudfront distribution has been deleted.