Pipeline support to python script

通过Jenkins pipeline实现调用python脚本，Pipeline使用Pipeline script from SCM具体实现参考以下代码：

echo "enable_build_package: ${enable_build_package}"

pipeline{
    agent { label "xxxxxxx" }
    stages{
        stage("Build Package"){
            when {
                expression {
                    if ( enable_build_package == "true" ){
                        echo "Build Package"
                        return true
                    }else{
                        echo "Skip Build Package"
                        return false
                    }
                }
            }
            steps{
                echo "Start Build Package"
            }
        }
        stage("Upload Package to Nexus"){
            when {
                expression {
                    if ( enable_upload_nexus == "true" ){
                        echo "Upload Package to Nexus"
                        return true
                    }else{
                        echo "Skip Upload Package to Nexus"
                        return false
                    }
                }
            }
            steps{
                echo "Start Upload Package to Nexus"
            }
        }
        stage("Running Tower Ansible for python script"){
            steps{
                 withCredentials([usernamePassword(credentialsId: 'xxxxxxx', passwordVariable: 'password', usernameVariable: 'username')]) {
                    sh '/usr/local/bin/python2.7 --version'
                    sh "/usr/local/bin/pip2.7 list"
                    sh "whereis virtualenv"
                    sh "/usr/local/bin/virtualenv env"
                    sh "ls env/bin"
                    echo "${workspace}"
                    sh 'env/bin/pip install requests -i https://xxxxxxx:8084/nexus/repository/pypi/simple --cert cert/truststore-2.0.11.pem'
                    sh "env/bin/pip list"
                    sh "env/bin/python script/tower_api.py --user ${username} --password ${password} --template allen"
                }

            }
        }
    }
}