=== modified file 'xl/version.py'
--- xl/version.py	2010-03-15 21:24:17 +0000
+++ xl/version.py	2010-03-16 19:58:48 +0000
@@ -38,9 +38,14 @@
     """
     try:
         import bzrlib.workingtree
+        import bzrlib.errors as errors
+    except ImportError:
+        return None
+
+    try:
         wt = bzrlib.workingtree.WorkingTree.open_containing(directory)[0]
         wt.lock_read()
-    except (errors.NoWorkingTree, errors.NotLocalUrl, ImportError):
+    except (errors.NoWorkingTree, errors.NotLocalUrl, errors.NotBranchError):
         return None
 
     revid = wt.last_revision()