Update Dockerfile

Dockerfile

@@ -20,7 +20,7 @@ ENV IPYTHONDIR=/app/ipython
 RUN mkdir -p /app/ipython && chmod -R 777 /app/ipython
 
 # Create an output folder and give it all permissions
-RUN mkdir -p /app/output && chmod -R 777 /app/output
+RUN mkdir -p /app/output && chmod -R 2777 /app/output
 
 # Install any needed packages specified in requirements.txt
 RUN pip install --no-cache-dir -r requirements.txt