Lab 3b - Gradle build failed

When executing the following step accroding to the Exercise Book:
`docker-compose -f docker-compose-clients.yml build`

The Gradle build fails with the following error code:

Building producer
Step 1/16 : FROM gradle:5.2.1-jdk11-slim AS builder
---> c36098ea188b
Step 2/16 : WORKDIR /home/gradle/project
---> Using cache
---> a78c92772b0d
Step 3/16 : COPY build.gradle ./
---> cbb681cca3f0 Step 4/16 : COPY settings.gradle ./
---> 5b5288f922a3 Step 5/16 : COPY producer.properties ./
---> 08c1e6f53f37
Step 6/16 : COPY src ./src
---> 9a0a3f3a4368
Step 7/16 : USER root
---> Running in 86a00b3a7862 Removing intermediate container 86a00b3a7862
---> bcfc6ac391ad
Step 8/16 : RUN gradle build
---> Running in 926d824b6d64

Welcome to Gradle 5.2.1!

Here are the highlights of this release:
- Define sets of dependencies that work together with Java Platform plugin
- New C++ plugins with dependency management built-in
- New C++ project types for gradle init
- Service injection into plugins and project extensions

For more details see https://docs.gradle.org/5.2.1/release-notes.html

Starting a Gradle Daemon (subsequent builds will be faster)

FAILURE: Build failed with an exception.

* Where:
Build file '/home/gradle/project/build.gradle' line: 2

* What went wrong:
Plugin [id: 'com.commercehub.gradle.plugin.avro', version: '1.0.0'] was not found in any of the following sources:

- Gradle Core Plugins (plugin is not in 'org.gradle' namespace)
- Plugin Repositories (could not resolve plugin artifact 'com.commercehub.gradle.plugin.avro:com.commercehub.gradle.plugin.avro.gradle.plugin:1.0.0')
Searched in the following repositories:
Gradle Central Plugin Repository
BintrayJCenter
JCenter Gradle Plugins(https://dl.bintray.com/gradle/gradle-plugins)

This prevents me from building a Producer or Consumer.

Run `docker-compose -f docker-compose-clients.yml build` to reproduce the failure. Inspect `build.gradle` at line 2 along with `settings.gradle`, then verify that both the Producer and Consumer builds complete successfully.

Written by the indexing model from the issue text.