/bin/sh: apt-get: not found

I am trying to change a dockerFile to work with aspell. I have a bash script that I want to wrap in a dock

Step 4: Wrap the script in a Docker container.

The sample SDK we downloaded earlier contains an example of an action wrapped in a Docker container. In particular, the sample SDK includes a Dockerfile that builds the C program in client/example.c and installs the binary as /blackbox/client/action .

The key line in the sample Dockerfile is:

RUN cd /blackbox/client; gcc -o action example.c

Instead of compiling example.c and installing the binary as an action, we’ll change the Dockerfile to install aspell into the Linux environment, and then install our action.sh script as the executable action command.

To do so, we delete the RUN command above, and insert the following commands into the Dockerfile:

RUN apt-get install -y aspell
RUN rm -f /blackbox/client/action
ADD action.sh /blackbox/client/action

I am trying to do this on the dockerfile below

# Dockerfile for example whisk docker action
FROM openwhisk/dockerskeleton

ENV FLASK_PROXY_PORT 8080

### Add source file(s)
ADD example.c /action/example.c

RUN sudo apt-get install -y aspell
RUN rm -f /blackbox/client/action
ADD action.sh /blackbox/client/action

CMD ["/home/huseyin/bin", "-c", "cd actionProxy && python -u actionproxy.py"]

The tutorial is outdated so I can't figure out how to make it work. What am I doing wrong?