This blog was written for fastai v1 and v2, please note that the latest version that released in 2019 Feb is v3.

The error that you get indicate you didn’t setup symlink correctly, that’s python telling you it does not know where is the fastai module is. Depends on if you are on Window or Linux, the command for setting up symlink are different. If you are on Linux, the setup script should already did the symlink for you.