问为什么Jenkins在运行sh‘’时返回并退出代码127？

EN

pipeline {
    agent {
        label 'python'
    }
    stages {
        stage ('Test') {
            steps {
                sh 'echo Aloha!!!!!'
            }
        }
        stage ('Is there any python?') {
            steps {
                sh 'python3 --version'
            }
        }
    }
}

FROM ubuntu:21.10

ARG DEBIAN_FRONTEND=noninteractive

RUN apt-get update && \
    apt-get install -qy git wget software-properties-common openssh-server && \
    sed -i 's|session    required     pam_loginuid.so|session    optional     pam_loginuid.so|g' /etc/pam.d/sshd && \
    mkdir -p /var/run/sshd && \
    apt-get install -qy openjdk-8-jdk && \
    apt-get install -qy maven && \
    apt-get install -qy apt-utils && \
    useradd -ms /bin/bash jenkins && \
    echo "jenkins:jenkins" | chpasswd && \
    mkdir /home/jenkins/.m2

RUN mkdir /home/jenkins/.ssh/ && \
    touch /home/jenkins/.ssh/authorized_keys

RUN chown -R jenkins:jenkins /home/jenkins/.m2/ && \
    chown -R jenkins:jenkins /home/jenkins/.ssh/

RUN apt-get install python3

RUN apt-get update && apt-get install python3-pip python3.9-venv -y

RUN cd "$(dirname $(which python3))" && \
    ln -s idle3 idle && \
    ln -s pydoc3 pydoc && \
    ln -s python3 python && \
    ln -s python3-config python-config

COPY .pypirc /home/jenkins/

EXPOSE 22

CMD ["/usr/sbin/sshd", "-D"]

[Pipeline] { (Is there any python?)
[Pipeline] sh
+ python3 --version
/var/jenkins_home/workspace/Jobs/Pipeline Github Example@tmp/durable-a28fa974/script.sh: 1: python3: not found
[Pipeline] }
[Pipeline] // stage
[Pipeline] }
[Pipeline] // withEnv
[Pipeline] }
[Pipeline] // node
[Pipeline] End of Pipeline
ERROR: script returned exit code 127
Finished: FAILURE