Make Travis CI use python 3

.travis.yml

@@ -8,6 +8,10 @@ sudo: false
 git:
   depth: 1
 
+before_install:
+- sudo apt-get update
+- sudo apt-get install python3
+
 # test-and-build does the installation, so tell travis to skip the
 # installation step
 install: true

scripts/test-and-build.sh

@@ -4,7 +4,7 @@ set -ex
 
 cd `dirname $0`/..
 
-virtualenv env
+virtualenv -p python3 env
 . env/bin/activate
 pip install -r scripts/requirements.txt