'Adds the block hash to the file tracker responsible for this vfs URN.'

@flow.StateHandler()
def CheckHash(self, responses):

    index = responses.request_data['index']
    if (index not in self.state.pending_files):
        return
    file_tracker = self.state.pending_files[index]
    hash_response = responses.First()
    if ((not responses.success) or (not hash_response)):
        urn = file_tracker['stat_entry'].pathspec.AFF4Path(self.client_id)
        self.Log(('Failed    to    read    %s:    %s' % (urn, responses.status)))
        self._FileFetchFailed(index, responses.request.request.name)
        return
    file_tracker.setdefault('hash_list', []).append(hash_response)
    self.state.blob_hashes_pending += 1
    if (self.state.blob_hashes_pending > self.MIN_CALL_TO_FILE_STORE):
        self.FetchFileContent()
