Error while enabling checkpoints in the Docker container.

```
Loading required package: checkpoint

checkpoint: Part of the Reproducible R Toolkit from Microsoft
https://mran.microsoft.com/documents/rro/reproducibility/
Error in authorizeFileSystemUse(checkpointLocation) : 
  The .checkpoint folder does not exist. Please try again after creating the folder at /root/.checkpoint
Calls: checkpoint -> authorizeFileSystemUse
Execution halted
```
