Fix travis as some dependency dropped python 2.6 support.

.travis.yml

@@ -33,7 +33,8 @@ install:
   - if [[ $TRAVIS_PYTHON_VERSION == '2.6' ]]; then conda create --yes -q -n pyenv mkl python=2.6 numpy=1.7.1 scipy=0.11 nose=1.3.0 pip flake8=2.3 six=1.9.0 pep8=1.6.2 pyflakes=0.8.1 sphinx; fi
   - if [[ $TRAVIS_PYTHON_VERSION == '3.3' ]]; then conda create --yes -q -n pyenv mkl python=3.3 numpy=1.9.1 scipy=0.14.0 nose=1.3.4 pip flake8=2.3 six=1.9.0 pep8=1.6.2 pyflakes=0.8.1 sphinx; fi
   - source activate pyenv
-  - if [[ $TRAVIS_PYTHON_VERSION == '2.6' ]]; then pip install pydot; else pip install pydot-ng; fi
+# pydot 1.2 broke support of python 2.6. They won't try to maintain it.
+  - if [[ $TRAVIS_PYTHON_VERSION == '2.6' ]]; then pip install pydot==1.1.0; else pip install pydot-ng; fi
   - pip install . --no-deps
   - pip install flake8-future-import nose-parameterized==0.5.0