debian: also build with python3
We build with Python 3 along with Python 2. The binary package will
contain the extension for both python version. This is to ease
transition until the mercurial package in Debian uses Python 3. The
documentation is still built with Python 2 because it needs Mercurial
(which is currently Python 2).
Doc is generated with sphinx.
You can generate the doc with:
```
make
```
# Tutorials
For updating the tutorials, you need to have the docgraph extension installed
(https://pypi.python.org/pypi/hg-docgraph).
Then run the test-topic-tutorial.t and test-tutorial.t to update the output if
needed.
You'll need the dot binary (likely installed by the graphviz package in your
package manager) in order to have graphviz graphs rendered in the html output.
Simply run make in the docs directory should takes care of the conversion of
the tutorial .t files into .rst files. Then sphinx should do the rest of the
jobs by rendering graphviz graphs.