ref(*): disable pip version check and caching

The constant reminders that pip has a new version are not
helpful to our build process, and some python libraries were
being inadvertently cached at /root/.cache/ inside Docker images.

Author: mboersma

Makefile

@@ -69,7 +69,7 @@ test: test-unit test-functional
 
 setup-venv:
 	@if [ ! -d venv ]; then virtualenv venv; fi
-	venv/bin/pip install -q -r requirements.txt -r dev_requirements.txt
+	venv/bin/pip install --disable-pip-version-check -q -r requirements.txt -r dev_requirements.txt
 
 test-style: setup-venv
 	venv/bin/flake8

build.sh

@@ -36,7 +36,7 @@ mkdir -p /app && chown -R deis:deis /app
 mkdir -p /templates && chown -R deis:deis /templates
 
 # install dependencies
-pip install -r /app/requirements.txt
+pip install --disable-pip-version-check --no-cache-dir -r /app/requirements.txt
 
 # cleanup.
 apk del --purge \