fixing up sphinx syntax.

docs/config.rst

@@ -10,7 +10,7 @@ Configuration variables are useful in a variety of situations, including:
 * choose whether to run in development mode
 * select the environment to run against
 
-.. code:: python
+.. code-block:: python
 
     # config.set_defaults can be used to set some default values.
     build.config.set_defaults({

docs/cookbook/reuse.rst

@@ -76,7 +76,7 @@ reuse. Supply an package in your index repository that contains
 all the tasks, and download it in your ubuild.py.
 
 
-.. code:: python
+.. code-block:: python
     # in a module mycompany_build
     import subprocess
     import uranium
@@ -104,7 +104,7 @@ all the tasks, and download it in your ubuild.py.
 
 And your consumer script will look like:
 
-.. code:: python
+.. code-block:: python
     # ubuild.py in the project.
     from uranium import get_remote_script
 

docs/envs.rst

@@ -8,7 +8,7 @@ lifetime of the build, but for any entry points or scripts generated as well.
 environment variables can be modified as a regular dictionary:
 
 
-.. code:: python
+.. code-block:: python
 
     import os