Trying fix travis 9. Add swig dependence

Author: pitbulk

.travis.yml

@@ -4,7 +4,7 @@ python:
 
 install:
   - sudo apt-get update -qq
-  - sudo apt-get install -qq python-dev libxml2-dev libxmlsec1-dev
+  - sudo apt-get install -qq swig python-dev libxml2-dev libxmlsec1-dev
   - 'travis_retry pip install .'
   - 'travis_retry pip install -e ".[test]"'