just install the package for python-lxml

... instead of trying to upgrade pip

Author: aparrish

.travis.yml

@@ -6,7 +6,7 @@ jdk: oraclejdk8
 
 before_install:
     - sudo apt-get update
-    - sudo apt-get install python python-pip git
+    - sudo apt-get install python python-pip git python-lxml
     - curl -L -O http://py.processing.org/processing.py-linux64.tgz
     - tar xfvz processing.py-linux64.tgz
     - cp processing.py-*-linux64/processing-py.jar .