anchor.diff:  
   # Install Python requirements
   COPY requirements.txt ./  
  -RUN pip install --no-cache-dir -r requirements.txt
  +RUN pip3 install --no-cache-dir -r requirements.txt
   
   # Copy Python app files
   COPY . ./
  
positive.code: FROM python:3.7
  
  # Create `worker` user and use it's home dir
  RUN useradd -m worker
  
negative.code: 
  # Run Celery as the user `worker`
  USER worker
  
  # Register executors as `worker` so that they can be discovered by Executa
  # It is necessary to do this again for the `worker` user because
  # the executors are not yet smart enough to register themselves
  # system wide when registered by a root user in the `FROM` image
  # and because we are using a different user.
  RUN basha register
  RUN node /usr/lib/node_modules/@stencila/encoda/dist/encoda.js register
  RUN python3 -m stencila.pyla register
  RUN R -e 'rasta::register()'
  
  CMD celery worker --app worker --queues stencila --hostname worker@stencila
  