Fix string/bytes issues under python 3. 1) cgi/client.py: override cgi.FieldStorage's make_file so that file is always created in binary/byte mode. This means that json (and xml) are bytes not strings. 2) rest.py: try harder to find dicttoxml in roundup directory or on sys.path. This just worked under python 2 but python 3 only searches sys.path by default and does not search relative like python 2. 3) rest.py: replace headers.getheader call removed from python 3 with equivalent code. 4) rest.py: make value returned from dispatch into bytes not string. 5) test/caseinsensitivedict.py, test/test_CaseInsensitiveDict.py: get code from stackoverflow that implements a case insensitive key dict. So dict['foo'], dict['Foo'] are the same entry. Used for looking up headers in mocked http rewuset header array. 6) test/rest_common.py: rework tests for etags and rest to properly supply bytes to the called routines. Calls to s2b and b2s and use of BytesIO and overriding make_file in cgi.FieldStorage to try to make sure it works under python 3.

import time, struct, base64
from roundup.cgi.actions import RegisterAction
from roundup.cgi.exceptions import *

def timestamp():
    return base64.encodestring(struct.pack("i", time.time())).strip()

def unpack_timestamp(s):
    return struct.unpack("i",base64.decodestring(s))[0]

class Timestamped:
    def check(self):
        try:
            created = unpack_timestamp(self.form['opaque'].value)
        except KeyError:
            raise FormError("somebody tampered with the form")
        if time.time() - created < 4:
            raise FormError("responding to the form too quickly")
        return True

class TimestampedRegister(Timestamped, RegisterAction):
    def permission(self):
        self.check()
        RegisterAction.permission(self)

def init(instance):
    instance.registerUtil('timestamp', timestamp)
    instance.registerAction('register', TimestampedRegister)