Use explicit exception to detect invalid path (BackReferenceError), see comments on r773

git-svn-id: http://pyfilesystem.googlecode.com/svn/trunk@775 67cdc799-7952-0410-af00-57a81ceafa0f

1 files changed, 5 insertions, 0 deletions

diff --git a/fs/errors.py b/fs/errors.py
index 38cb4b7..93f8905 100644
--- a/fs/errors.py
+++ b/fs/errors.py
@@ -188,6 +188,11 @@ class NoMMapError(ResourceError):
     default_message = "Can't get mmap for %(path)s"
 
 
+class BackReferenceError(FSError, ValueError):
+    """Exception raised when too many backrefs exist in a path (ex: '/..', '/docs/../..')."""
+    default_message = "Too many backrefs in '%(path)s'"
+
+
 def convert_fs_errors(func):
     """Function wrapper to convert FSError instances into OSError."""
     @wraps(func)