spring-boot: Spring Boot reference documentation - Build failure

I am following the instructions under “Building reference documentation” in the README of the “Master” branch at: https://github.com/spring-projects/spring-boot

Having cloned the source repository, I run the first Maven command: $ ./mvnw clean install -pl spring-boot-tools/spring-boot-maven-plugin -Pdefault,full This succeeds.

Then I try the second Maven command: $ ./mvnw clean install -pl spring-boot-docs -Pdefault,full This eventually fails with the following error:

[INFO] --- maven-dependency-plugin:2.10:unpack (unpack-starter-poms) @ spring-boot-docs ---
[INFO] Configured Artifact: org.springframework.boot:spring-boot-starters:starter-poms:1.4.0.BUILD-SNAPSHOT:zip
Downloading: http://repo.spring.io/snapshot/org/springframework/boot/spring-boot-starters/1.4.0.BUILD-SNAPSHOT/spring-boot-starters-1.4.0.BUILD-SNAPSHOT-starter-poms.zip
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 08:28 min
[INFO] Finished at: 2016-04-08T13:15:14+10:00
[INFO] Final Memory: 55M/278M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-dependency-plugin:2.10:unpack (unpack-starter-poms) on project spring-boot-docs: Unable to find artifact. Could not find artifact org.springframework.boot:spring-boot-starters:zip:starter-poms:1.4.0.BUILD-SNAPSHOT in spring-snapshots (http://repo.spring.io/snapshot)
[ERROR]
[ERROR] Try downloading the file manually from the project website.
[ERROR]
[ERROR] Then, install it using the command:
[ERROR] mvn install:install-file -DgroupId=org.springframework.boot -DartifactId=spring-boot-starters -Dversion=1.4.0.BUILD-SNAPSHOT -Dclassifier=starter-poms -Dpackaging=zip -Dfile=/path/to/file
[ERROR]
[ERROR] Alternatively, if you host your own repository you can deploy the file there:
[ERROR] mvn deploy:deploy-file -DgroupId=org.springframework.boot -DartifactId=spring-boot-starters -Dversion=1.4.0.BUILD-SNAPSHOT -Dclassifier=starter-poms -Dpackaging=zip -Dfile=/path/to/file -Durl=[url] -DrepositoryId=[id]
[ERROR]
[ERROR]
[ERROR] org.springframework.boot:spring-boot-starters:zip:1.4.0.BUILD-SNAPSHOT
[ERROR]
[ERROR] from the specified remote repositories:
[ERROR] spring-ext (http://repo.spring.io/ext-release-local/, releases=true, snapshots=false),
[ERROR] spring-milestones (http://repo.spring.io/milestone, releases=true, snapshots=false),
[ERROR] spring-snapshots (http://repo.spring.io/snapshot, releases=true, snapshots=true),
[ERROR] central (https://repo.maven.apache.org/maven2, releases=true, snapshots=false)

I’ve tried to find the relevant file to download and install manually (as suggested in the error message) but to no avail.

Any assistance greatly appreciated.