This is a code block:

.. code-block:: python

  y += 1

After this text is a code block that goes boom:

.. code-block:: python

  raise Exception('boom!')

Now we have an invisible code block, great for setting things up or checking
stuff within a doc:


.. invisible-code-block: python

  z += 1

This paranoidly checks that we can use binary and unicode literals:

.. code-block:: python

  bin = b'x'
  uni = u'x'
