[enh] utils/lib.sh - commands pyenv, pyenv.drop pyenv.(un)install

Implement a boilerplate to manage performance optimized virtualenv builds.
Shell scripts can use (e.g.) 'pyenv.cmd' to execute command in the virtualenv
without having to worry about whether and how the environment is provided. ::

  pyenv.cmd which python
  ..../local/py3/bin/python

  pyenv.cmd which pip
  ..../local/py3/bin/pip

If pyenv.cmd released multiple times the installation will only rebuild if the
function 'pyenv.OK' fails.  Function 'pyenv.OK' make some test to validate that
the virtualenv exists and works as expected.  The check also fails if
requirements listed requirements-dev.txt and requirements.txt has been edited.
Among these tests 'pyenv.OK' calls 'pyenv.check' which implements a python
script that validate the python installation.  Here is an example how a
'pyenv.check' implementation could look like::

    pyenv.check() {
       cat  <<EOF
    import yaml
    print('import yaml --> OK')
    EOF
    }

Signed-off-by: Markus Heiser <markus@darmarit.de>

utils/lib.sh

@@ -86,7 +86,7 @@ set_terminal_colors() {
     _Red='\e[0;31m'
     _Green='\e[0;32m'
     _Yellow='\e[0;33m'
-    _Blue='\e[0;34m'
+    _Blue='\e[0;94m'
     _Violet='\e[0;35m'
     _Cyan='\e[0;36m'
 
@@ -95,12 +95,12 @@ set_terminal_colors() {
     _BRed='\e[1;31m'
     _BGreen='\e[1;32m'
     _BYellow='\e[1;33m'
-    _BBlue='\e[1;34m'
+    _BBlue='\e[1;94m'
     _BPurple='\e[1;35m'
     _BCyan='\e[1;36m'
 }
 
-if [ ! -p /dev/stdout ]; then
+if [ ! -p /dev/stdout ] && [ ! "$TERM" = 'dumb' ] && [ ! "$TERM" = 'unknown' ]; then
     set_terminal_colors
 fi
 
@@ -152,6 +152,12 @@ err_msg()  { echo -e "${_BRed}ERROR:${_creset} $*" >&2; }
 warn_msg() { echo -e "${_BBlue}WARN:${_creset}  $*" >&2; }
 info_msg() { echo -e "${_BYellow}INFO:${_creset}  $*" >&2; }
 
+build_msg() {
+    local tag="$1        "
+    shift
+    echo -e "${_Blue}${tag:0:10}${_creset}$*"
+}
+
 clean_stdin() {
     if [[ $(uname -s) != 'Darwin' ]]; then
         while read -r -n1 -t 0.1; do : ; done
@@ -496,6 +502,203 @@ service_is_available() {
     return "$exit_val"
 }
 
+# python
+# ------
+
+PY="${PY:=3}"
+PYTHON="${PYTHON:=python$PY}"
+PY_ENV="${PY_ENV:=local/py${PY}}"
+PY_ENV_BIN="${PY_ENV}/bin"
+PY_ENV_REQ="${PY_ENV_REQ:=${REPO_ROOT}/requirements*.txt}"
+
+# List of python packages (folders) or modules (files) installed by command:
+# pyenv.install
+PYOBJECTS="${PYOBJECTS:=.}"
+
+# folder where the python distribution takes place
+PYDIST="${PYDIST:=dist}"
+
+# folder where the intermediate build files take place
+PYBUILD="${PYBUILD:=build/py${PY}}"
+
+# https://www.python.org/dev/peps/pep-0508/#extras
+#PY_SETUP_EXTRAS='[develop,test]'
+PY_SETUP_EXTRAS="${PY_SETUP_EXTRAS:=[develop,test]}"
+
+PIP_BOILERPLATE=( pip wheel setuptools )
+
+# shellcheck disable=SC2120
+pyenv() {
+
+    # usage:  pyenv [vtenv_opts ...]
+    #
+    #   vtenv_opts: see 'pip install --help'
+    #
+    # Builds virtualenv with 'requirements*.txt' (PY_ENV_REQ) installed.  The
+    # virtualenv will be reused by validating sha256sum of the requirement
+    # files.
+
+    required_commands \
+        sha256sum "${PYTHON}" \
+        || exit
+
+    local pip_req=()
+
+    if ! pyenv.OK > /dev/null; then
+        rm -f "${PY_ENV}/${PY_ENV_REQ}.sha256"
+        pyenv.drop > /dev/null
+        build_msg PYENV "[virtualenv] installing ${PY_ENV_REQ} into ${PY_ENV}"
+
+        "${PYTHON}" -m venv "$@" "${PY_ENV}"
+        "${PY_ENV_BIN}/python" -m pip install -U "${PIP_BOILERPLATE[@]}"
+
+        for i in ${PY_ENV_REQ}; do
+            pip_req=( "${pip_req[@]}" "-r" "$i" )
+        done
+
+        (
+            [ "$VERBOSE" = "1" ] && set -x
+            # shellcheck disable=SC2086
+            "${PY_ENV_BIN}/python" -m pip install "${pip_req[@]}" \
+                && sha256sum ${PY_ENV_REQ} > "${PY_ENV}/requirements.sha256"
+        )
+    fi
+    pyenv.OK
+}
+
+_pyenv_OK=''
+pyenv.OK() {
+
+    # probes if pyenv exists and runs the script from pyenv.check
+
+    [ "$_pyenv_OK" == "OK" ] && return 0
+
+    if [ ! -f "${PY_ENV_BIN}/python" ]; then
+        build_msg PYENV "[virtualenv] missing ${PY_ENV_BIN}/python"
+        return 1
+    fi
+
+    if [ ! -f "${PY_ENV}/requirements.sha256" ] \
+        || ! sha256sum --check --status <"${PY_ENV}/requirements.sha256" 2>/dev/null; then
+        build_msg PYENV "[virtualenv] requirements.sha256 failed"
+        sed 's/^/          [virtualenv] - /' <"${PY_ENV}/requirements.sha256"
+        return 1
+    fi
+
+    pyenv.check \
+        | "${PY_ENV_BIN}/python" 2>&1 \
+        | prefix_stdout "${_Blue}PYENV     ${_creset}[check] "
+
+    local err=${PIPESTATUS[1]}
+    if [ "$err" -ne "0" ]; then
+        build_msg PYENV "[check] python test failed"
+        return "$err"
+    fi
+
+    build_msg PYENV "OK"
+    _pyenv_OK="OK"
+    return 0
+}
+
+pyenv.drop() {
+
+    build_msg PYENV "[virtualenv] drop ${PY_ENV}"
+    rm -rf "${PY_ENV}"
+    _pyenv_OK=''
+
+}
+
+pyenv.check() {
+
+    # Prompts a python script with additional checks. Used by pyenv.OK to check
+    # if virtualenv is ready to install python objects.  This function should be
+    # overwritten by the application script.
+
+    local imp=""
+
+    for i in "${PIP_BOILERPLATE[@]}"; do
+        imp="$imp, $i"
+    done
+
+    cat  <<EOF
+import ${imp#,*}
+
+EOF
+}
+
+pyenv.install() {
+
+    if ! pyenv.OK; then
+        py.clean > /dev/null
+    fi
+    if ! pyenv.install.OK > /dev/null; then
+        build_msg PYENV "[install] ${PYOBJECTS}"
+        if ! pyenv.OK >/dev/null; then
+            pyenv
+        fi
+        for i in ${PYOBJECTS}; do
+    	    build_msg PYENV "[install] pip install -e '$i${PY_SETUP_EXTRAS}'"
+    	    "${PY_ENV_BIN}/python" -m pip install -e "$i${PY_SETUP_EXTRAS}"
+        done
+    fi
+    pyenv.install.OK
+}
+
+_pyenv_install_OK=''
+pyenv.install.OK() {
+
+    [ "$_pyenv_install_OK" == "OK" ] && return 0
+
+    local imp=""
+    local err=""
+
+    if [ "." = "${PYOBJECTS}" ]; then
+        imp="import $(basename "$(pwd)")"
+    else
+        # shellcheck disable=SC2086
+        for i in ${PYOBJECTS}; do imp="$imp, $i"; done
+        imp="import ${imp#,*} "
+    fi
+    (
+        [ "$VERBOSE" = "1" ] && set -x
+        "${PY_ENV_BIN}/python" -c "import sys; sys.path.pop(0); $imp;" 2>/dev/null
+    )
+
+    err=$?
+    if [ "$err" -ne "0" ]; then
+        build_msg PYENV "[install] python installation test failed"
+        return "$err"
+    fi
+
+    build_msg PYENV "[install] OK"
+    _pyenv_install_OK="OK"
+    return 0
+}
+
+pyenv.uninstall() {
+
+    build_msg PYENV "[uninstall] ${PYOBJECTS}"
+
+    if [ "." = "${PYOBJECTS}" ]; then
+	pyenv.cmd python setup.py develop --uninstall 2>&1 \
+            | prefix_stdout "${_Blue}PYENV     ${_creset}[pyenv.uninstall] "
+    else
+	pyenv.cmd python -m pip uninstall --yes ${PYOBJECTS} 2>&1 \
+            | prefix_stdout "${_Blue}PYENV     ${_creset}[pyenv.uninstall] "
+    fi
+}
+
+
+pyenv.cmd() {
+    pyenv.install
+    (   set -e
+        # shellcheck source=/dev/null
+        source "${PY_ENV_BIN}/activate"
+        [ "$VERBOSE" = "1" ] && set -x
+        "$@"
+    )
+}
+
 # golang
 # ------
 
@@ -1250,7 +1453,7 @@ pkg_install() {
 	centos)
             # shellcheck disable=SC2068
             yum install -y $@
-            ;;    
+            ;;
     esac
 }
 
@@ -1382,6 +1585,10 @@ LXC_ENV_FOLDER=
 if in_container; then
     # shellcheck disable=SC2034
     LXC_ENV_FOLDER="lxc-env/$(hostname)/"
+    PY_ENV="${LXC_ENV_FOLDER}${PY_ENV}"
+    PY_ENV_BIN="${LXC_ENV_FOLDER}${PY_ENV_BIN}"
+    PYDIST="${LXC_ENV_FOLDER}${PYDIST}"
+    PYBUILD="${LXC_ENV_FOLDER}${PYBUILD}"
 fi
 
 lxc_init_container_env() {