'Get confirmation from user to delete an index.
This method will enter an input loop until the user provides a
response it is expecting.  Valid input is one of three responses:
y: Confirm deletion of index.
n: Do not delete index.
a: Delete all indexes without asking for further confirmation.
If the user enters nothing at all, the default action is to skip
that index and do not delete.
If the user selects \'a\', as a side effect, the \'force\' flag is set.
Args:
index: Index to confirm.
Returns:
True if user enters \'y\' or \'a\'.  False if user enter \'n\'.'

def GetConfirmation(self, index):

    while True:
        print 'This    index    is    no    longer    defined    in    your    index.yaml    file.'
        print
        print index.ToYAML()
        print
        confirmation = self.confirmation_fn('Are    you    sure    you    want    to    delete    this    index?    (N/y/a):    ')
        confirmation = confirmation.strip().lower()
        if (confirmation == 'y'):
            return True
        elif ((confirmation == 'n') or (not confirmation)):
            return False
        elif (confirmation == 'a'):
            self.force = True
            return True
        else:
            print 'Did    not    understand    your    response.'
