Add python stage helper

README.md

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+# pipelineUtils
+
+This project is an attempt to provide a structured set of functions that can be used to create a pipeline library for the Jenkins CI/CD system.
+
+## Overview
+
+Functions provided fall into several categories:
+
+- "stage" helpers that implment a stage in the pipeline with particular behavior.
+- "versioning" helpers that implement a particular strategy for versioning a project.
+- "utiltity" functions that help with various things, such as printing banners in the job console log, incrementing a semantic version string, and adding git meta information to a pipeline's metadata.
+
+## Example

vars/pythonVenvStage.groovy

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+i
+
+void call(Map config = [:], Closure body) {
+    defaultConfig = [
+        pythonPath: 'python3',
+        recreateVenv: false,
+        venvDir: '.venv',
+        updatePip: true,
+        installPipTools: true,
+        requirementsFile: 'requirements.in',
+        name: 'python'
+    ]
+    runConfig = defaultConfig + config
+
+    venvDir = [
+      env.WORKSPACE,
+      runConfig.venvDir
+    ]
+    venvBinDir = venvDir + 'bin'
+    venvPython = venvBinDir + 'python'
+
+    venvEnv = [
+      "VIRTUAL_ENV=${venvDir.join('/')}",
+      "PATH=${venvBinDir.join('/')}"
+    ]
+
+    stage(runConfig.name) {
+            if (fileExists(runConfig.venvDir) && runConfig.recreateVenv)  {
+            dir(runConfig.venvDir) {
+                deleteDir()
+            }
+        }
+
+        if (!fileExists(runConfig.venvDir)) {
+            sh "${runConfig.pythonPath} -m venv ${runConfig.venvDir}"
+        }
+
+        withEnv(venvEnv) {
+            if (runConfig.updatePip) {
+                sh "${venvPython} -m pip install --upgrade pip"
+            }
+            if (runConfig.installPipTools) {
+                sh "${venvPython} -m pip install pip-tools"
+            }
+            if (fileExists(runConfig.requirementsFile)) {
+                sh "pip-compile ${runConfig.requirementsFile}"
+            }
+            body()
+        }
+    }
+}