Designate should 400 on a SPF record data with trailing backlash

To reproduce, post an SPF recordset where the record data ends in a trailing slash:

{
  "name" : "foospf.example.com.",
  "description" : "An SPF recordset.",
  "type" : "SPF",
  "ttl" : 3600,
  "records" : [
      "v=spf1 +all\\"
    ]
}

The recordset will not 400 like it should. It will go to an ERROR status. Looking at mini dns logs, I see:

2016-02-10 23:46:55.326 TRACE designate.service Traceback (most recent call last):
2016-02-10 23:46:55.326 TRACE designate.service File "/root/designate/designate/service.py", line 332, in _dns_handle
2016-02-10 23:46:55.326 TRACE designate.service {'payload': payload, 'addr': addr}):
2016-02-10 23:46:55.326 TRACE designate.service File "/root/designate/designate/dnsutils.py", line 137, in __call__
2016-02-10 23:46:55.326 TRACE designate.service for response in self.application(message):
2016-02-10 23:46:55.326 TRACE designate.service File "/root/designate/designate/mdns/handler.py", line 75, in __call__
2016-02-10 23:46:55.326 TRACE designate.service for response in self._handle_axfr(request):
2016-02-10 23:46:55.326 TRACE designate.service File "/root/designate/designate/mdns/handler.py", line 303, in _handle_axfr
2016-02-10 23:46:55.326 TRACE designate.service [str(record[4])], # rdata
2016-02-10 23:46:55.326 TRACE designate.service File "/root/designate/.venv/local/lib/python2.7/site-packages/dns/rrset.py", line 134, in from_text_list
2016-02-10 23:46:55.326 TRACE designate.service rd = dns.rdata.from_text(r.rdclass, r.rdtype, t)
2016-02-10 23:46:55.326 TRACE designate.service File "/root/designate/.venv/local/lib/python2.7/site-packages/dns/rdata.py", line 449, in from_text
2016-02-10 23:46:55.326 TRACE designate.service return cls.from_text(rdclass, rdtype, tok, origin, relativize)
2016-02-10 23:46:55.326 TRACE designate.service File "/root/designate/.venv/local/lib/python2.7/site-packages/dns/rdtypes/txtbase.py", line 48, in from_text
2016-02-10 23:46:55.326 TRACE designate.service token = tok.get().unescape()
2016-02-10 23:46:55.326 TRACE designate.service File "/root/designate/.venv/local/lib/python2.7/site-packages/dns/tokenizer.py", line 398, in get
2016-02-10 23:46:55.326 TRACE designate.service raise dns.exception.UnexpectedEnd
2016-02-10 23:46:55.326 TRACE designate.service UnexpectedEnd
2016-02-10 23:46:55.326 TRACE designate.service

This is running with bind + agent, on commit commit b16fadeb801766dbbd3a15754f5f2530c191e7e2.

The expected behavior here is to 400 on SPF records with trailing slashes.

Also, see these functional test logs: See these functional test logs: http://logs.openstack.org/49/278549/1/check/gate-designate-dsvm-bind9/7a59e02/console.html#_2016-02-10_20_03_31_057