linkage-checker-enforcer-rules incompatible with maven 3.9? ClassNotFound: org/eclipse/aether/connector/basic/BasicRepositoryConnectorFactory

Start with the minimal pom.xml in the issue and reproduce the linkage-check execution using Maven 3.9.* and 3.8.9. Investigate why linkage-checker-enforcer-rules 1.5.15 cannot load BasicRepositoryConnectorFactory under Maven 3.9; done means the check runs without the missing-class failure on the affected Maven versions.

I am trying to get the plugin working with a minimal pom.xml:

<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>it.neckar</groupId>
  <artifactId>test-project</artifactId>
  <version>1.0-SNAPSHOT</version>
  <packaging>jar</packaging>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
    <dependency>
      <groupId>org.junit.jupiter</groupId>
      <artifactId>junit-jupiter</artifactId>
      <version>5.10.0</version>
      <scope>test</scope>
    </dependency>
  </dependencies>

  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-enforcer-plugin</artifactId>
        <version>3.6.2</version>

        <dependencies>
          <dependency>
            <groupId>com.google.cloud.tools</groupId>
            <artifactId>linkage-checker-enforcer-rules</artifactId>
            <version>1.5.15</version>
          </dependency>
        </dependencies>

        <executions>
          <execution>
            <id>linkage-check</id>
            <goals>
              <goal>enforce</goal>
            </goals>
            <phase>verify</phase>
            <configuration>
              <rules>
                <LinkageCheckerRule
                  implementation="com.google.cloud.tools.dependencies.enforcer.LinkageCheckerRule" />
              </rules>
              <fail>true</fail>
            </configuration>
          </execution>
        </executions>
      </plugin>
    </plugins>
  </build>

</project>

Execution linkage-check of goal org.apache.maven.plugins:maven-enforcer-plugin:3.6.2:enforce failed: A required class was missing while executing org.apache.maven.plugins:maven-enforcer-plugin:3.6.2:enforce: org/eclipse/aether/connector/basic/BasicRepositoryConnectorFactory

It fails with

• mvn 3.9.*

Works up until

• mvn 3.8.9