ref: DanielStutzbach/blist#90

blist is used for its sortedlist in ruletypes.py and appears to be abandonware - might I suggest that the SortedKeyList [0] from python-sortedcontainers [1] could replace it?

[0] http://www.grantjenks.com/docs/sortedcontainers/introduction.html#sorted-key-list
[1] https://github.com/grantjenks/python-sortedcontainers