Use virtualenv for building

So the virtualenv-does-not-belong-in-container argument is null and
void! (SamYaple eyes ayoung...)

Due to the deps we have we end up installing python-requests from the
package manager. This leads to `pip wheel` failing to build because the
installed version of requests is too old. A venv solves this problem
(and removes the need for hash -r).

A venv should *not* be needed for project containers since the deps are
isolated. But should deps interfere we may be forced into venvs in the
project containers later. For now, it is isolated to builds.

Change-Id: Id38a115ba925fd6930789ed65db64f6e3709af3e
Depends-On: I453f8ecbb41cda3bb68ebc7ae5f5198ca9c9d772

centos/Dockerfile

@@ -1,6 +1,7 @@
 FROM centos:7
 
-ENV PROJECT=requirements
+ENV PROJECT=requirements \
+    PATH=/builder/bin:$PATH
 ARG PROJECT_REPO=https://git.openstack.org/openstack/${PROJECT}
 ARG PROJECT_REF=master
 ARG OVERRIDE=override
@@ -35,6 +36,7 @@ RUN set -x \
         python \
         python-devel \
         python-pip \
+        python-virtualenv \
         libgcrypt \
         nss-util \
         systemd-devel \
@@ -43,7 +45,9 @@ RUN set -x \
     && git --git-dir /tmp/requirements/.git fetch --depth 1 $PROJECT_REPO $PROJECT_REF \
     && git --work-tree /tmp/requirements --git-dir /tmp/requirements/.git checkout FETCH_HEAD \
     && mv /tmp/requirements/global-requirements.txt /tmp/requirements/upper-constraints.txt /root/packages/ \
-    && pip install -U pip wheel setuptools \
+    && python -m virtualenv /builder \
+    && pip install -U pip \
+    && pip install -U wheel setuptools \
     # NOTE(SamYaple): There is a bug with python-nss, this is a workaround. https://bugzilla.redhat.com/show_bug.cgi?id=1389739
     && sed -i '/dogtag-pki/d' /root/packages/global-requirements.txt \
     && pip download -d /tmp -c /root/packages/upper-constraints.txt python-nss \

debian/Dockerfile

@@ -1,6 +1,7 @@
 FROM debian:jessie-slim
 
-ENV PROJECT=requirements
+ENV PROJECT=requirements \
+    PATH=/builder/bin:$PATH
 ARG PROJECT_REPO=https://git.openstack.org/openstack/${PROJECT}
 ARG PROJECT_REF=master
 ARG OVERRIDE=override
@@ -31,14 +32,15 @@ RUN set -x \
         pkg-config \
         python-dev \
         python-pip \
+        python-virtualenv \
     && mkdir /root/packages \
     && git init /tmp/requirements \
     && git --git-dir /tmp/requirements/.git fetch --depth 1 $PROJECT_REPO $PROJECT_REF \
     && git --work-tree /tmp/requirements --git-dir /tmp/requirements/.git checkout FETCH_HEAD \
     && mv /tmp/requirements/global-requirements.txt /tmp/requirements/upper-constraints.txt /root/packages/ \
-    && pip install -U pip wheel setuptools \
-    # TODO(pbourke): 'hash -r' should no longer be required once we move to stretch
-    && hash -r \
+    && python -m virtualenv /builder \
+    && pip install -U pip \
+    && pip install -U wheel setuptools \
     # NOTE(SamYaple): There is a bug with python-nss, this is a workaround. https://bugzilla.redhat.com/show_bug.cgi?id=1389739
     && sed -i '/dogtag-pki/d' /root/packages/global-requirements.txt \
     && pip download -d /tmp -c /root/packages/upper-constraints.txt python-nss \

ubuntu/Dockerfile

@@ -1,6 +1,7 @@
 FROM ubuntu:xenial
 
-ENV PROJECT=requirements
+ENV PROJECT=requirements \
+    PATH=/builder/bin:$PATH
 ARG PROJECT_REPO=https://git.openstack.org/openstack/${PROJECT}
 ARG PROJECT_REF=master
 ARG OVERRIDE=override
@@ -31,12 +32,15 @@ RUN set -x \
         python \
         python-dev \
         python-pip \
+        python-virtualenv \
     && mkdir /root/packages \
     && git init /tmp/requirements \
     && git --git-dir /tmp/requirements/.git fetch --depth 1 $PROJECT_REPO $PROJECT_REF \
     && git --work-tree /tmp/requirements --git-dir /tmp/requirements/.git checkout FETCH_HEAD \
     && mv /tmp/requirements/global-requirements.txt /tmp/requirements/upper-constraints.txt /root/packages/ \
-    && pip install -U pip wheel setuptools \
+    && python -m virtualenv /builder \
+    && pip install -U pip \
+    && pip install -U wheel setuptools \
     # NOTE(SamYaple): There is a bug with python-nss, this is a workaround. https://bugzilla.redhat.com/show_bug.cgi?id=1389739
     && sed -i '/dogtag-pki/d' /root/packages/global-requirements.txt \
     && pip download -d /tmp -c /root/packages/upper-constraints.txt python-nss \