Getting a non existent file fails with 500

[diocas]

A GET to a non existent file, on a folder that also does not exists, should not fail:

Error while reading container: /my/path/test.txt error listing container: path:"/my/path/"
    Traceback (most recent call last):
      File "/Users/dalvesde/Workspace/proj-swan/dev-qa-update/cs3api4lab/cs3api4lab/api/cs3apismanager.py", line 91, in file_exists
        cs3_container = self.file_api.read_directory(parent_path, self.cs3_config.endpoint)
      File "/Users/dalvesde/Workspace/proj-swan/dev-qa-update/cs3api4lab/cs3api4lab/api/cs3_file_api.py", line 194, in read_directory
        raise IOError(res.status.message)
    OSError: error listing container: path:"/my/path/"