Fix tests for python 3

.travis.yml

@@ -9,4 +9,4 @@ install:
     - "pip install pyfakefs"
     - "python setup.py install"
 # command to run tests
-script: nosetests
+script: python -m unittest discover

tests/__init__.py

@@ -0,0 +1,4 @@
+import sys, os
+
+this_dir = os.path.dirname(os.path.abspath(__file__))
+sys.path.insert(0, this_dir)