[exception] add InvalidSlice exception

Author: jgrewe

nixio/exceptions/__init__.py

@@ -1,6 +1,6 @@
 from .exceptions import (DuplicateName, UninitializedEntity, InvalidUnit,
                          InvalidAttrType, InvalidEntity, OutOfBounds,
-                         IncompatibleDimensions, InvalidFile,
+                         IncompatibleDimensions, InvalidFile, InvalidSlice,
                          DuplicateColumnName, UnsupportedLinkType)
 
 __all__ = (

nixio/exceptions/exceptions.py

@@ -47,6 +47,13 @@ def __init__(self, *args, **kwargs):
         super(InvalidEntity, self).__init__(self.message, *args, **kwargs)
 
 
+class InvalidSlice(Exception):
+
+    def __init__(self, *args, **kwargs):
+        self.message = "Trying to access data with an invalid slice."
+        super(InvalidSlice, self).__init__(self.message, *args, **kwargs)
+
+
 class OutOfBounds(IndexError):
 
     def __init__(self, message, index=None):