The Cloud9 workspace should be built by an IAM user with Administrator privileges, not the root account user. Please ensure you are logged in as an IAM user, not the root account user.
Go to Cloud9 Console
Select the region where you will be running this workshop from the Top menu in case no region is selected by default.
Select Create environment
airflow-workshop, and select Next Step
Stick with the default settings, and select Next Step
Lastly, select Create Environment
When it comes up, customize the environment by closing the welcome tab and lower work area, and opening a new terminal tab in the main work area:
Your workspace should now look like this:
If you like this theme, you can choose it yourself by selecting View / Themes / Solarized / Solarized Dark in the Cloud9 workspace menu.