Explicitly use "classic" theme on Sphinx 1.3+

"default" was renamed to "classic" in 1.3; as of 1.3.1, it still points
to the same theme but gives a warning (the implication is that
"alabaster" will become default in the future). This change ensures
consistency going forward and compatibility with older distro packages,
unless we decide to depend on another theme.

Author: welshjf

doc/conf.py

@@ -16,7 +16,9 @@
 DESCRIPTION = 'The Swiss Army Knife of the Bitcoin protocol.'
 AUTHORS = 'The python-bitcoinlib developers'
 
-import sys, os
+import sphinx
+import sys
+import os
 
 # If extensions (or modules to document with autodoc) are in another directory,
 # add these directories to sys.path here. If the directory is relative to the
@@ -107,7 +109,10 @@
 
 # The theme to use for HTML and HTML Help pages.  See the documentation for
 # a list of builtin themes.
-html_theme = 'default'
+if getattr(sphinx, 'version_info', (0, 0)) >= (1, 3):
+    html_theme = 'classic'
+else:
+    html_theme = 'default'
 
 # Theme options are theme-specific and customize the look and feel of a theme
 # further.  For a list of options available for each theme, see the