=== modified file 'shell.py'
--- shell.py	2011-04-27 00:00:18 +0000
+++ shell.py	2012-03-07 07:32:58 +0000
@@ -132,6 +132,10 @@
         self.set_prompt()
 
     def set_prompt(self):
+        try:
+            self.tree = WorkingTree.open_containing('.')[0]
+        except:
+            self.tree = None
         if self.tree is not None:
             try:
                 prompt_data = (self.tree.branch.nick, self.tree.branch.revno(),