It looks like you're trying to compile the most recent branch, with a version that hasn't been released yet. For Gazebo 9 for example, try doing this first in your clone directory:

hg up gazebo9

The tutorial has a note about this, "Note: the default branch is the development branch where you'll find the bleeding edge code, your cloned repository should be on this branch by default but we recommend you switch to the gazebo6 branch if you desire more stability," but maybe we could be a bit more explicit with instructions.