TST: Use pgcollections.OrderedDict for 2.6 compat

.travis.yml

@@ -65,6 +65,11 @@ install:
     - 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

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
 
-files = utils.buildFileList(utils.examples)
+# 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:

pyqtgraph/parametertree/SystemSolver.py

@@ -1,4 +1,4 @@
-from collections import OrderedDict
+from ..pgcollections import OrderedDict
 import numpy as np
 
 class SystemSolver(object):