Travis: Bump PyPy version and install with external script

.travis.yml

@@ -9,19 +9,22 @@ matrix:
   include:
     # Test on pypy without coverage, because it's unnecessary and very slow.
     - python: "pypy"
-      env: PYPY_VERSION="4.0.1" NO_COVERAGE="1"
+      env: PYPY_VERSION="5.3.1" NO_COVERAGE="1"
 
 cache:
   directories:
     - $HOME/.cache/pip
-    - $HOME/downloads
+    - $HOME/.pyenv_cache
 services:
   - redis-server
 
 before_install:
   # If necessary, set up an appropriate version of pypy.
-  - if [ ! -z "$PYPY_VERSION" ]; then source utils/setup-pypy-travis.sh; fi
-  - if [ ! -z "$PYPY_VERSION" ]; then python --version 2>&1 | fgrep "PyPy $PYPY_VERSION"; fi
+  - |
+      if [[ -n "$PYPY_VERSION" ]]; then
+        wget https://github.com/praekeltfoundation/travis-pypy/releases/download/0.1.0/setup-pypy.sh
+        source setup-pypy.sh
+      fi
 install:
   # Update pip because Travis has 6.x which doesn't cache wheels
   - "pip install pip>=8.0.0"