[#589] Fixes DeprecationWarning on ckan.lib.app_globals

Instead of calling config.debug, we need to call config['debug'].

Fixes #589.

ckan/lib/app_globals.py

@@ -71,7 +71,7 @@ def set_main_css(css_file):
     ''' Sets the main_css using debug css if needed.  The css_file
     must be of the form file.css '''
     assert css_file.endswith('.css')
-    if config.debug and css_file == '/base/css/main.css':
+    if ('debug' in config) and (css_file == '/base/css/main.css'):
         new_css = '/base/css/main.debug.css'
     else:
         new_css = css_file