Document how $ and % can be escaped in configparser.
my_dir: %(home_dir)s/lumberjack
my_pictures: %(my_dir)s/Pictures
+ [Escape]
+ gain: 80%% # use a %% to escape the % sign (% is the only character that needs to be escaped)
In the example above, :class:`ConfigParser` with *interpolation* set to
``BasicInterpolation()`` would resolve ``%(home_dir)s`` to the value of
my_dir: ${home_dir}/lumberjack
my_pictures: ${my_dir}/Pictures
+ [Escape]
+ cost: $$80 # use a $$ to escape the $ sign ($ is the only character that needs to be escaped)
+
Values from other sections can be fetched as well:
.. code-block:: ini