Remove unused exception

 o class WillNotSchedule(CinderException):

   This exception was removed in the following commit.

    commit cea7fe21cecfcd28ede3ba411b8ab8b36c9a7c15
    Author: Zhiteng Huang <zhithuang@ebaysf.com>
    Date:   Thu Jan 2 15:44:30 2014 +0800

        Drop Chance/SimpleScheduler Implementation

Change-Id: I8f5f8e6c5c844a67607dae9fb63524aef7069133
Merge "Remove unused exception"
(Test commit) Change README to reflect Jio's fork of Cinder

Change-Id: I3f26c0a736e63725aec24ca2fa12c707b8e6460f