Fix crash in owners.py.

BUG=none
TEST=none

Review URL: https://chromiumcodereview.appspot.com/10383038

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@135806 0039d316-1c4b-4281-b951-d872f2087c98

owners.py

@@ -215,6 +215,7 @@ class Database(object):
       # Remove all directories owned by the current owner from the remaining
       # list.
       for dirname in owned_dirs[max_owner]:
-        dirs.remove(dirname)
+        if dirname in dirs:
+          dirs.remove(dirname)
 
     return final_owners