#18852: Handle readline.__doc__ being None in site.py readline activation.

Patch by Berker Peksag.
diff --git a/Lib/site.py b/Lib/site.py
index 77d198a..c4ea6f6 100644
--- a/Lib/site.py
+++ b/Lib/site.py
@@ -388,8 +388,9 @@
             return
 
         # Reading the initialization (config) file may not be enough to set a
-        # completion key, so we set one first and then read the file
-        if 'libedit' in getattr(readline, '__doc__', ''):
+        # completion key, so we set one first and then read the file.
+        readline_doc = getattr(readline, '__doc__', '')
+        if readline_doc is not None and 'libedit' in readline_doc:
             readline.parse_and_bind('bind ^I rl_complete')
         else:
             readline.parse_and_bind('tab: complete')