diff --git a/.travis.yml b/.travis.yml
index de5ac94d..e90828f0 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,7 +17,7 @@ env:
     # Enable python 2 and python 3 builds
     # Note that the 2.6 build doesn't get flake8, and runs old versions of
     # Pyglet and GLFW to make sure we deal with those correctly
-    #- PYTHON=2.6 QT=pyqt TEST=standard
+    - PYTHON=2.6 QT=pyqt TEST=standard
     - PYTHON=2.7 QT=pyqt TEST=extra
     - PYTHON=2.7 QT=pyside TEST=standard
     - PYTHON=3.4 QT=pyqt TEST=standard
@@ -30,7 +30,7 @@ before_install:
     - chmod +x miniconda.sh
     - ./miniconda.sh -b -p /home/travis/mc
     - export PATH=/home/travis/mc/bin:$PATH
-    
+
     # not sure what is if block is for
     - if [ "${TRAVIS_PULL_REQUEST}" != "false" ]; then
           GIT_TARGET_EXTRA="+refs/heads/${TRAVIS_BRANCH}";
@@ -55,7 +55,7 @@ install:
     - echo ${QT}
     - echo ${TEST}
     - echo ${PYTHON}
-    
+
     - if [ "${QT}" == "pyqt" ]; then
           conda install pyqt --yes;
       fi;
@@ -64,7 +64,12 @@ install:
       fi;
     - pip install pytest-xdist # multi-thread py.test
     - pip install pytest-cov # add coverage stats
-    
+
+    # required for example testing on python 2.6
+    - if [ "${PYTHON}" == "2.6" ]; then
+        pip install importlib;
+      fi;
+
     # Debugging helpers
     - uname -a
     - cat /etc/issue
@@ -79,7 +84,7 @@ before_script:
     - export DISPLAY=:99.0
     - "sh -e /etc/init.d/xvfb start"
     - /sbin/start-stop-daemon --start --quiet --pidfile /tmp/custom_xvfb_99.pid --make-pidfile --background --exec /usr/bin/Xvfb -- :99 -screen 0 1400x900x24 -ac +extension GLX +render
-    
+
     # Make sure everyone uses the correct python (this is handled by conda)
     - which python
     - python --version
@@ -127,16 +132,16 @@ before_script:
       fi;
 
 script:
-  
+
     - source activate test_env
-    
+
     # Run unit tests
     - start_test "unit tests";
-      PYTHONPATH=. py.test --cov pyqtgraph -n 4 -sv;
+      PYTHONPATH=. py.test --cov pyqtgraph -sv;
       check_output "unit tests";
     - echo "test script finished. Current directory:"
     - pwd
-    
+
     # check line endings
     - if [ "${TEST}" == "extra" ]; then
         start_test "line ending check";
@@ -166,13 +171,13 @@ script:
     - start_test "install test";
       python setup.py --quiet install;
       check_output "install test";
-    
+
     # Check double-install fails
     # Note the bash -c is because travis strips off the ! otherwise.
     - start_test "double install test";
       bash -c "! python setup.py --quiet install";
       check_output "double install test";
-      
+
     # Check we can import pg
     - start_test "import test";
       echo "import sys; print(sys.path)" | python &&
diff --git a/examples/test_examples.py b/examples/test_examples.py
index 0f9929ca..3e6b8200 100644
--- a/examples/test_examples.py
+++ b/examples/test_examples.py
@@ -1,15 +1,20 @@
 from __future__ import print_function, division, absolute_import
 from pyqtgraph import Qt
-from examples import utils
-import importlib
+from . import utils
 import itertools
 import pytest
 
+# apparently importlib does not exist in python 2.6...
+try:
+    import importlib
+except ImportError:
+    # we are on python 2.6
+    print("If you want to test the examples, please install importlib from "
+          "pypi\n\npip install importlib\n\n")
+    pass
+
 files = utils.buildFileList(utils.examples)
-
 frontends = {Qt.PYQT4: False, Qt.PYSIDE: False}
-# frontends = {Qt.PYQT4: False, Qt.PYQT5: False, Qt.PYSIDE: False}
-
 # sort out which of the front ends are available
 for frontend in frontends.keys():
     try:
@@ -25,7 +30,7 @@ def test_examples(frontend, f):
     # Test the examples with all available front-ends
     print('frontend = %s. f = %s' % (frontend, f))
     if not frontends[frontend]:
-        pytest.skip('{} is not installed. Skipping tests'.format(frontend))
+        pytest.skip('%s is not installed. Skipping tests' % frontend)
     utils.testFile(f[0], f[1], utils.sys.executable, frontend)
 
 if __name__ == "__main__":
diff --git a/pyqtgraph/parametertree/SystemSolver.py b/pyqtgraph/parametertree/SystemSolver.py
index 0a889dfa..24e35e9a 100644
--- a/pyqtgraph/parametertree/SystemSolver.py
+++ b/pyqtgraph/parametertree/SystemSolver.py
@@ -1,4 +1,4 @@
-from collections import OrderedDict
+from ..pgcollections import OrderedDict
 import numpy as np
 
 class SystemSolver(object):
diff --git a/pyqtgraph/tests/test_stability.py b/pyqtgraph/tests/test_stability.py
index 7582d353..810b53bf 100644
--- a/pyqtgraph/tests/test_stability.py
+++ b/pyqtgraph/tests/test_stability.py
@@ -34,7 +34,7 @@ itemTypes = [
 
 widgets = []
 items = []
-allWidgets = weakref.WeakSet()
+allWidgets = weakref.WeakKeyDictionary()
 
 
 def crashtest():
@@ -99,7 +99,7 @@ def createWidget():
     widget = randItem(widgetTypes)()
     widget.setWindowTitle(widget.__class__.__name__)
     widgets.append(widget)
-    allWidgets.add(widget)
+    allWidgets[widget] = 1
     p("    %s" % widget)
     return widget