Script will fail if certain directories do not exist

[atc6955]

If these directories do not already exist, the script will fail.

/var/www/
/etc/nginx/sites-available/

Error message:
mkdir: cannot create directory ‘/var/www/saleor-api.user.domain’: No such file or directory

[Orianas]

I think this is mainly taken care of by the fact that you should have setup Nginx before hand. Those directories will be created along the way. But, I think instead of failing it would probably be better to test first and suggest installation.