Only install module mappings once.

src/allmydata/__init__.py

@@ -37,3 +37,8 @@ __appname__ = "tahoe-lafs"
 # in the "application" part of the Tahoe versioning scheme:
 # https://tahoe-lafs.org/trac/tahoe-lafs/wiki/Versioning
 __full_version__ = __appname__ + '/' + str(__version__)
+
+
+# Install Python 3 module locations in Python 2:
+from future import standard_library
+standard_library.install_aliases()

src/allmydata/test/test_humanreadable.py

@@ -4,14 +4,14 @@ from __future__ import absolute_import
 from __future__ import division
 from __future__ import print_function
 
-from future import standard_library
-standard_library.install_aliases()
 from past.builtins import long
+
 from twisted.trial import unittest
 
 from allmydata.util import humanreadable
 
 
+
 def foo(): pass # keep the line number constant
 
 

src/allmydata/util/humanreadable.py

@@ -2,8 +2,6 @@ from __future__ import division
 from __future__ import absolute_import
 from __future__ import print_function
 from __future__ import unicode_literals
-from future import standard_library
-standard_library.install_aliases()
 
 import os
 from reprlib import Repr