fix platform.sh build using virtualenv

Author: robfrawley

.gitignore

@@ -1,3 +1,5 @@
 /_build/doctrees
 /_build/html
+/.venv/
+/.idea/
 *.pyc

.platform.app.yaml

@@ -43,13 +43,16 @@ web:
 # The size of the persistent disk of the application (in MB).
 disk: 512
 
-# Build time dependencies.
 dependencies:
   python:
-    sphinx: "1.3.6"
+    virtualenv: "15.1"
 
 # The hooks that will be performed when the package is deployed.
 hooks:
     build: |
-      pip install git+https://github.com/fabpot/sphinx-php.git
-      make -C _build html
+        virtualenv .venv
+        . .venv/bin/activate
+        export PIP_USER=
+        pip install pip==9.0.1 wheel==0.29.0
+        pip install -r _build/.requirements.txt
+        make -C _build html

_build/.requirements.txt

@@ -0,0 +1 @@
+git+https://github.com/fabpot/sphinx-php.git@master#egg_name=sphinx-php