checking for GTK3... no
GTK 3 >= 3.0.1 not found

Missing dependencies.
Taking a look to README.packages we can see that some devel packages are needed for Fedora and OpenSuse with GTK3. Please test in Ubuntu if these are the missing dependencies, and I will update the file.

sudo apt-get install gtk3-devel gtksourceview3-devel
sudo apt-get install libgtksourceview3.0-dev

I've forgotten that now configure sets GTK3 by default, sorry about that.