address the review (mostly)

src/allmydata/test/common_util.py

@@ -1,6 +1,6 @@
 from __future__ import print_function
 
-import os, signal
+import os
 from random import randrange
 from six.moves import StringIO
 

src/allmydata/test/test_util.py

@@ -5,7 +5,7 @@ from __future__ import unicode_literals
 
 from future.utils import PY2
 if PY2:
-    from builtins import zip, str, range, object
+    from future.builtins import filter, map, zip, ascii, chr, hex, input, next, oct, pow, round, super, bytes, dict, int, list, object, range, str, max, min  # noqa: F401from builtins import range
 import binascii
 import six
 import os, time, sys

src/allmydata/util/fileutil.py

@@ -1,3 +1,9 @@
+"""
+Ported to Python3
+
+Futz with files like a pro.
+"""
+
 from __future__ import print_function
 from __future__ import absolute_import
 from __future__ import division
@@ -7,11 +13,6 @@ from future.utils import PY2
 if PY2:
     # open is not here because we want to use native strings on Py2
     from future.builtins import filter, map, zip, ascii, chr, hex, input, next, oct, pow, round, super, bytes, dict, int, list, object, range, str, max, min  # noqa: F401from builtins import range
-"""
-Ported to Python3
-
-Futz with files like a pro.
-"""
 
 import sys, os, stat, tempfile, time, binascii
 import six

src/allmydata/util/spans.py

@@ -7,10 +7,6 @@ from future.utils import PY2
 if PY2:
     from builtins import filter, map, zip, ascii, chr, hex, input, next, oct, open, pow, round, super, bytes, dict, int, list, object, range, str, max, min  # noqa: F401
 
-from future.utils import PY2
-if PY2:
-    from future.builtins import object
-
 
 class Spans(object):
     """I represent a compressed list of booleans, one per index (an integer).

src/allmydata/util/statistics.py

@@ -20,8 +20,6 @@ from future.utils import PY2
 if PY2:
     from builtins import filter, map, zip, ascii, chr, hex, input, next, oct, open, pow, round, super, bytes, dict, int, list, object, range, str, max, min  # noqa: F401
 
-from functools import reduce
-
 from allmydata.util.mathutil import round_sigfigs
 import math
 from functools import reduce