add empty docstrings for exceptions

riakcached/exceptions.py

@@ -1,23 +1,46 @@
 class RiakcachedException(Exception):
+    """
+    """
     pass
 
+
 class RiakcachedBadRequest(RiakcachedException):
+    """
+    """
     pass
 
+
 class RiakcachedNotFound(RiakcachedException):
+    """
+    """
     pass
 
+
 class RiakcachedServiceUnavailable(RiakcachedException):
+    """
+    """
     pass
 
+
 class RiakcachedPreconditionFailed(RiakcachedException):
+    """
+    """
     pass
 
+
 class RiakcachedConflict(RiakcachedException):
+    """
+    """
     pass
 
+
 class RiakcachedTimeout(RiakcachedException):
+    """
+    """
     pass
 
+
 class RiakcachedConnectionError(RiakcachedException):
+    """
+    """
     pass