Adds contrib/requirements/py26.txt (importlib)

contrib/requirements/py26.txt

@@ -0,0 +1 @@
+importlib

tox.ini

@@ -28,6 +28,7 @@ commands = pip -E {envdir} install -r contrib/requirements/default.txt
 [testenv:py26]
 basepython = python2.6
 commands = pip -E {envdir} install -r contrib/requirements/default.txt
+           pip -E {envdir} install -r contrib/requirements/py26.txt
            pip -E {envdir} install -r contrib/requirements/test.txt
            nosetests --with-xunit --xunit-file=nosetests.xml \
                      --with-coverage3  --cover3-xml          \