fix travis to test 5.2

.travis.yml

@@ -1,21 +1,25 @@
 language: python
+dist: xenial
 python: 2.7
 sudo: false
 cache:
+  pip: true
   directories:
     - eggs
-env:
-  - PLONE_VERSION=5.0
-  - PLONE_VERSION=5.1
 matrix:
-  allow_failures:
+  include:
+    - env: PLONE_VERSION=5.0
+      python: "2.7"
     - env: PLONE_VERSION=5.1
+      python: "2.7"
+    - env: PLONE_VERSION=5.2
+      python: "2.7"
+    - env: PLONE_VERSION=5.2
+      python: "3.7"
   fast_finish: true
 install:
   - sed -ie "s#test-5.0#test-$PLONE_VERSION#" buildout.cfg
-  - pip install setuptools==33.1.1
-  - pip install zc.buildout==2.8.0
-  - buildout bootstrap .
-  - bin/buildout annotate
-  - bin/buildout -Nv install test
+  - pip install -r https://dist.plone.org/release/$PLONE_VERSION-latest/requirements.txt
+  - buildout annotate
+  - buildout -Nv install test
 script: bin/test