diff --git a/src/allmydata/test/common_py3.py b/src/allmydata/test/common_py3.py
index f917cf8fb..0dae05aa6 100644
--- a/src/allmydata/test/common_py3.py
+++ b/src/allmydata/test/common_py3.py
@@ -12,17 +12,12 @@ from __future__ import print_function
 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, list, object, range, str, max, min  # noqa: F401
-from past.builtins import unicode
 
 import os
 import time
 import signal
 
 from twisted.internet import reactor
-from twisted.trial import unittest
-
-from ..util.assertutil import precondition
-from ..util.encodingutil import unicode_platform, get_filesystem_encoding
 
 
 class TimezoneMixin(object):
@@ -70,20 +65,3 @@ class SignalMixin(object):
         if self.sigchldHandler:
             signal.signal(signal.SIGCHLD, self.sigchldHandler)
         return super(SignalMixin, self).tearDown()
-
-
-class ReallyEqualMixin(object):
-    def failUnlessReallyEqual(self, a, b, msg=None):
-        self.assertEqual(a, b, msg)
-        self.assertEqual(type(a), type(b), "a :: %r (%s), b :: %r (%s), %r" % (a, type(a), b, type(b), msg))
-
-
-def skip_if_cannot_represent_filename(u):
-    precondition(isinstance(u, unicode))
-
-    enc = get_filesystem_encoding()
-    if not unicode_platform():
-        try:
-            u.encode(enc)
-        except UnicodeEncodeError:
-            raise unittest.SkipTest("A non-ASCII filename could not be encoded on this platform.")
diff --git a/src/allmydata/test/common_util.py b/src/allmydata/test/common_util.py
index 3b81be109..ce6271399 100644
--- a/src/allmydata/test/common_util.py
+++ b/src/allmydata/test/common_util.py
@@ -10,15 +10,23 @@ from twisted.trial import unittest
 
 from ..util.assertutil import precondition
 from ..scripts import runner
-from allmydata.util.encodingutil import get_io_encoding
+from allmydata.util.encodingutil import unicode_platform, get_filesystem_encoding, get_io_encoding
 # Imported for backwards compatibility:
 from future.utils import bord, bchr, binary_type
 from past.builtins import unicode
-from .common_py3 import (
-    SignalMixin, skip_if_cannot_represent_filename, ReallyEqualMixin
-)
+from .common_py3 import SignalMixin
 
 
+def skip_if_cannot_represent_filename(u):
+    precondition(isinstance(u, unicode))
+
+    enc = get_filesystem_encoding()
+    if not unicode_platform():
+        try:
+            u.encode(enc)
+        except UnicodeEncodeError:
+            raise unittest.SkipTest("A non-ASCII filename could not be encoded on this platform.")
+
 def skip_if_cannot_represent_argv(u):
     precondition(isinstance(u, unicode))
     try:
@@ -80,6 +88,12 @@ def flip_one_bit(s, offset=0, size=None):
     return result
 
 
+class ReallyEqualMixin(object):
+    def failUnlessReallyEqual(self, a, b, msg=None):
+        self.assertEqual(a, b, msg)
+        self.assertEqual(type(a), type(b), "a :: %r (%s), b :: %r (%s), %r" % (a, type(a), b, type(b), msg))
+
+
 class StallMixin(object):
     def stall(self, res=None, delay=1):
         d = defer.Deferred()
diff --git a/src/allmydata/test/test_encodingutil.py b/src/allmydata/test/test_encodingutil.py
index 376bd6ec6..cbc9143b7 100644
--- a/src/allmydata/test/test_encodingutil.py
+++ b/src/allmydata/test/test_encodingutil.py
@@ -77,7 +77,7 @@ from twisted.trial import unittest
 
 from twisted.python.filepath import FilePath
 
-from allmydata.test.common_py3 import (
+from allmydata.test.common_util import (
     ReallyEqualMixin, skip_if_cannot_represent_filename,
 )
 from allmydata.util import encodingutil, fileutil