Fix broken PyPy build.

... by installing an updated setuptools version.

modified:   .travis.yml

.travis.yml

@@ -8,6 +8,7 @@ python:
     - "pypy"
     - "pypy3.3-5.2-alpha1"
 install:
+    - pip install -U setuptools
     - pip install zc.buildout
     - buildout bootstrap
     - buildout