@@ -28,10 +28,13 @@ declare -A PROJECT_VENV

 # Get the path to the pip command.

 # get_pip_command

 function get_pip_command {

-    which pip || which pip-python

+    local version="$1"

+    # NOTE(dhellmann): I don't know if we actually get a pip3.4-python

+    # under any circumstances.

+    which pip${version} || which pip${version}-python

     if [ $? -ne 0 ]; then

-        die $LINENO "Unable to find pip; cannot continue"

+        die $LINENO "Unable to find pip${version}; cannot continue"

     fi

 }

@@ -66,6 +69,13 @@ function pip_install_gr {

     pip_install $clean_name

 }

+# Determine the python versions supported by a package

+function get_python_versions_for_package {

+    local name=$1

+    cd $name && python setup.py --classifiers \

+        | grep 'Language' | cut -f5 -d: | grep '\.' | tr '\n' ' '

+}

+

 # Wrapper for ``pip install`` to set cache and proxy environment variables

 # Uses globals ``OFFLINE``, ``PIP_VIRTUAL_ENV``,

 # ``PIP_UPGRADE``, ``TRACK_DEPENDS``, ``*_proxy``,

@@ -104,8 +114,22 @@ function pip_install {

             local sudo_pip="env"

         else

             local cmd_pip

-            cmd_pip=$(get_pip_command)

+            cmd_pip=$(get_pip_command $PYTHON2_VERSION)

             local sudo_pip="sudo -H"

+            if python3_enabled; then

+                # Look at the package classifiers to find the python

+                # versions supported, and if we find the version of

+                # python3 we've been told to use, use that instead of the

+                # default pip

+                local package_dir=${!#}

+                local python_versions

+                if [[ -d "$package_dir" ]]; then

+                    python_versions=$(get_python_versions_for_package $package_dir)

+                    if [[ $python_versions =~ $PYTHON3_VERSION ]]; then

+                        cmd_pip=$(get_pip_command $PYTHON3_VERSION)

+                    fi

+                fi

+            fi

         fi

     fi

@@ -113,6 +137,8 @@ function pip_install {

     # Always apply constraints

     cmd_pip="$cmd_pip -c $REQUIREMENTS_DIR/upper-constraints.txt"

+    # FIXME(dhellmann): Need to force multiple versions of pip for

+    # packages like setuptools?

     local pip_version

     pip_version=$(python -c "import pip; \

                         print(pip.__version__.strip('.')[0])")

@@ -276,6 +302,21 @@ function setup_package {

     fi

 }

+# Report whether python 3 should be used

+function python3_enabled {

+    if [[ $USE_PYTHON3 == "True" ]]; then

+        return 0

+    else

+        return 1

+    fi

+}

+

+# Install python3 packages

+function install_python3 {

+    if is_ubuntu; then

+        apt_get install python3.4 python3.4-dev

+    fi

+}

 # Restore xtrace

 $INC_PY_TRACE

@@ -19,6 +19,7 @@

 function stack_install_service {

     local service=$1

     if type install_${service} >/dev/null 2>&1; then

+        # FIXME(dhellmann): Needs to be python3-aware at some point.

         if [[ ${USE_VENV} = True && -n ${PROJECT_VENV[$service]:-} ]]; then

             rm -rf ${PROJECT_VENV[$service]}

             source $TOP_DIR/tools/build_venv.sh ${PROJECT_VENV[$service]} ${ADDITIONAL_VENV_PACKAGES//,/ }

@@ -118,6 +118,17 @@ if [[ -r $RC_DIR/.localrc.password ]]; then

     source $RC_DIR/.localrc.password

 fi

+# Control whether Python 3 should be used.

+export USE_PYTHON3=${USE_PYTHON3:-False}

+

+# When Python 3 is supported by an application, adding the specific

+# version of Python 3 to this variable will install the app using that

+# version of the interpreter instead of 2.7.

+export PYTHON3_VERSION=${PYTHON3_VERSION:-3.4}

+

+# Just to be more explicit on the Python 2 version to use.

+export PYTHON2_VERSION=${PYTHON2_VERSION:-2.7}

+

 # allow local overrides of env variables, including repo config

 if [[ -f $RC_DIR/localrc ]]; then

     # Old-style user-supplied config

@@ -8,6 +8,7 @@

 # Assumptions:

 # - update pip to $INSTALL_PIP_VERSION

+# - if USE_PYTHON3=True, PYTHON3_VERSION refers to a version already installed

 set -o errexit

 set -o xtrace

@@ -31,6 +32,8 @@ GetDistro

 echo "Distro: $DISTRO"

 function get_versions {

+    # FIXME(dhellmann): Deal with multiple python versions here? This

+    # is just used for reporting, so maybe not?

     PIP=$(which pip 2>/dev/null || which pip-python 2>/dev/null || true)

     if [[ -n $PIP ]]; then

         PIP_VERSION=$($PIP --version | awk '{ print $2}')

@@ -75,6 +78,9 @@ function install_get_pip {

         touch $LOCAL_PIP.downloaded

     fi

     sudo -H -E python $LOCAL_PIP

+    if python3_enabled; then

+        sudo -H -E python${PYTHON3_VERSION} $LOCAL_PIP

+    fi

 }

@@ -114,6 +120,7 @@ get_versions

 # python in f23 depends on the python-pip package

 if ! { is_fedora && [[ $DISTRO == "f23" ]]; }; then

     uninstall_package python-pip

+    uninstall_package python3-pip

 fi

 install_get_pip

@@ -122,6 +129,7 @@ if [[ -n $PYPI_ALTERNATIVE_URL ]]; then

     configure_pypi_alternative_url

 fi

+set -x

 pip_install -U setuptools

 get_versions

@@ -81,6 +81,9 @@ if [[ -n "$SYSLOG" && "$SYSLOG" != "False" ]]; then

     fi

 fi

+if python3_enabled; then

+    install_python3

+fi

 # Mark end of run

 # ---------------