Try Travis support suggestion for py3

Hi Christopher,

Thank you for reaching out and sorry to hear about the troubles.

Regarding the pip3 error, it was indeed caused by our image updates. We've cleaned-up the way we set-up the Python environment and now strictly enforce Python version use using pyenv. Which means that if you want to use a different Python version than the system one (which is 2.7.6), you have to explicitly specify it. Adding a "before_install: pyenv global 3.5" step to your travis.yml should switch the system version and make pip3 work without installing any additional packages.

Author: cdunn2001

.travis.yml

@@ -6,6 +6,7 @@
 # http://stackoverflow.com/questions/22111549/travis-ci-with-clang-3-4-and-c11/30925448#30925448
 # to allow C++11, though we are not yet building with -std=c++11
 
+before_install: pyenv global 3.5
 install:
 - if [[ $TRAVIS_OS_NAME == osx ]]; then
      brew update;
@@ -38,7 +39,6 @@ addons:
     - g++-4.9
     - clang-3.5
     - valgrind
-    - python3
 os:
   - linux
 language: cpp