Arvados

The bug is when a read-only collection has been spilled from the cache and then needs to be reloaded:

2016-04-04 10:25:02 arvados.arvados_fuse[10263] DEBUG: Updating None
2016-04-04 10:25:02 arvados.arvados_fuse[10263] ERROR: arv-mount b1eb3a7572b5fbbf04335bbf0ade7209+85: error
Traceback (most recent call last):
  File "/home/peter/work/scripts/venv/local/lib/python2.7/site-packages/arvados_fuse-0.1.20160322160927-py2.7.egg/arvados_fuse/fusedir.py", line 410, in update
    self.collection.update()
  File "/home/peter/work/scripts/venv/local/lib/python2.7/site-packages/arvados_python_client-0.1.20160322001610-py2.7.egg/arvados/arvfile.py", line 238, in synchronized_wrapper
    return orig_func(self, *args, **kwargs)
  File "/home/peter/work/scripts/venv/local/lib/python2.7/site-packages/arvados_python_client-0.1.20160322001610-py2.7.egg/arvados/retry.py", line 153, in num_retries_setter
    return orig_func(self, *args, **kwargs)
  File "/home/peter/work/scripts/venv/local/lib/python2.7/site-packages/arvados_python_client-0.1.20160322001610-py2.7.egg/arvados/collection.py", line 1228, in update
    self.apply(baseline.diff(other))
  File "/home/peter/work/scripts/venv/local/lib/python2.7/site-packages/arvados_python_client-0.1.20160322001610-py2.7.egg/arvados/arvfile.py", line 389, in must_be_writable_wrapper
    raise IOError(errno.EROFS, "Collection is read-only.")
IOError: [Errno 30] Collection is read-only.

reviewing 55778ad90a9b869f514e729b3f85c12383f4e2a7

I'm confused about if clear() should return a boolean or not...

because:

(class Directory) clear() line 166 does a

   if not oldentries[n].clear(force)

and _entries dict could contain a CollectionDirectory correct?

if that's the case code should be something like:

    def clear(self, force=False):
        rtn = super(CollectionDirectoryBase, self).clear(force)
        self.collection = None
        return rtn

and tests should include more complex examples of a full Directory._entries