Disable gce boto plugins by overriding BOTO_CONFIG

These plugins are not compatible with python 3 and breaking unit tests

.travis.yml

@@ -2,6 +2,8 @@ sudo: required
 language: python
 addons:
   postgresql: "9.5"
+env:
+  - BOTO_CONFIG=''
 python:
   - "2.7"
   - "3.4"

acceptance_tests.sh

@@ -13,4 +13,4 @@ curl -L https://github.com/coreos/etcd/releases/download/v${ETCDVERSION}/etcd-v$
 sudo pip2.7 install lettuce python-Levenshtein
 sudo pip2.7 install -r requirements-py2.txt
 
-lettuce
+exec lettuce