Set PATH to include the venv's bin
MODIFY
singleuser-builder/Dockerfile
singleuser-builder/Dockerfile
@@ -5,6 +5,7 @@ MAINTAINER Yuvi Panda <yuvipanda@gmail.com>
LABEL io.openshift.s2i.scripts-url=image:///usr/libexec/s2i
ENV APP_DIR /srv/app
+ENV PATH ${APP_DIR}/venv/bin:$PATH
RUN apt-get update && \
apt-get install --yes --no-install-recommends \

Set PATH to include the venv's bin