Maven site plugin or one of it's dependencies could not be resolved

Question

I am in a restricted network which doesn't allow access to dowloading files from the internet, as a result we have a local Nexus server running.

Whitelisting proxies is not an option

I need to update our common java libraries repository, I have managed to create a process for uploading new artifacts to nexus.

1. Use a settings.xml which allows connection to central
2. Download all new artifacts using a pom with the new dependencies declared
3. This downloads all jars/poms to ~/.m2/repository. I have a python script which copies the contents of repository to another temporary directory, it then walks this directory and runs mvn deploy:deploy-file for each jar/pom it comes across.
4. I then switch my settings.xml with one which only allows connection to nexus and not central.

In theory this sounded great but when I run mvn dependency:resolve with the local settings.xml I get the following

[INFO] Scanning for projects...
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-clean-plugin/2.5/maven-clean-plugin-2.5.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-clean-plugin/2.5/maven-clean-plugin-2.5.pom (4 KB at 23.2 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-plugins/22/maven-plugins-22.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-plugins/22/maven-plugins-22.pom (13 KB at 187.3 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/maven-parent/21/maven-parent-21.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/maven-parent/21/maven-parent-21.pom (26 KB at 357.5 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/apache/10/apache-10.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/apache/10/apache-10.pom (15 KB at 147.5 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-clean-plugin/2.5/maven-clean-plugin-2.5.jar
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-clean-plugin/2.5/maven-clean-plugin-2.5.jar (25 KB at 325.1 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-install-plugin/2.4/maven-install-plugin-2.4.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-install-plugin/2.4/maven-install-plugin-2.4.pom (7 KB at 100.5 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-plugins/23/maven-plugins-23.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-plugins/23/maven-plugins-23.pom (9 KB at 149.7 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/maven-parent/22/maven-parent-22.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/maven-parent/22/maven-parent-22.pom (30 KB at 215.2 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/apache/11/apache-11.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/apache/11/apache-11.pom (15 KB at 278.2 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-install-plugin/2.4/maven-install-plugin-2.4.jar
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-install-plugin/2.4/maven-install-plugin-2.4.jar (27 KB at 355.7 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-deploy-plugin/2.7/maven-deploy-plugin-2.7.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-deploy-plugin/2.7/maven-deploy-plugin-2.7.pom (6 KB at 91.4 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-deploy-plugin/2.7/maven-deploy-plugin-2.7.jar
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-deploy-plugin/2.7/maven-deploy-plugin-2.7.jar (27 KB at 494.4 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-site-plugin/3.3/maven-site-plugin-3.3.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-site-plugin/3.3/maven-site-plugin-3.3.pom (21 KB at 312.7 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-plugins/24/maven-plugins-24.pom
[WARNING] Failed to retrieve plugin descriptor for org.apache.maven.plugins:maven-site-plugin:3.3: Plugin org.apache.maven.plugins:maven-site-plugin:3.3 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-site-plugin:jar:3.3
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-antrun-plugin/1.3/maven-antrun-plugin-1.3.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-antrun-plugin/1.3/maven-antrun-plugin-1.3.pom (5 KB at 81.1 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-plugins/12/maven-plugins-12.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-plugins/12/maven-plugins-12.pom (12 KB at 47.6 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/maven-parent/9/maven-parent-9.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/maven-parent/9/maven-parent-9.pom (33 KB at 305.4 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/apache/4/apache-4.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/apache/4/apache-4.pom (5 KB at 75.7 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-antrun-plugin/1.3/maven-antrun-plugin-1.3.jar
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-antrun-plugin/1.3/maven-antrun-plugin-1.3.jar (24 KB at 451.4 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-assembly-plugin/2.2-beta-5/maven-assembly-plugin-2.2-beta-5.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-assembly-plugin/2.2-beta-5/maven-assembly-plugin-2.2-beta-5.pom (15 KB at 185.0 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-plugins/16/maven-plugins-16.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-plugins/16/maven-plugins-16.pom (13 KB at 252.9 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/maven-parent/15/maven-parent-15.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/maven-parent/15/maven-parent-15.pom (24 KB at 366.3 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/apache/6/apache-6.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/apache/6/apache-6.pom (13 KB at 137.3 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-assembly-plugin/2.2-beta-5/maven-assembly-plugin-2.2-beta-5.jar
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-assembly-plugin/2.2-beta-5/maven-assembly-plugin-2.2-beta-5.jar (204 KB at 2193.2 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-dependency-plugin/2.8/maven-dependency-plugin-2.8.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-dependency-plugin/2.8/maven-dependency-plugin-2.8.pom (12 KB at 116.5 KB/sec)
[WARNING] Failed to retrieve plugin descriptor for org.apache.maven.plugins:maven-dependency-plugin:2.8: Plugin org.apache.maven.plugins:maven-dependency-plugin:2.8 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-dependency-plugin:jar:2.8
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-release-plugin/2.3.2/maven-release-plugin-2.3.2.pom
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-release-plugin/2.3.2/maven-release-plugin-2.3.2.pom (10 KB at 116.5 KB/sec)
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/release/maven-release/2.3.2/maven-release-2.3.2.pom
[WARNING] Failed to retrieve plugin descriptor for org.apache.maven.plugins:maven-release-plugin:2.3.2: Plugin org.apache.maven.plugins:maven-release-plugin:2.3.2 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-release-plugin:jar:2.3.2
Downloading: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-metadata.xml
Downloading: http://localhost:8082/nexus/content/groups/public/org/codehaus/mojo/maven-metadata.xml
Downloaded: http://localhost:8082/nexus/content/groups/public/org/codehaus/mojo/maven-metadata.xml (834 B at 6.7 KB/sec)
Downloaded: http://localhost:8082/nexus/content/groups/public/org/apache/maven/plugins/maven-metadata.xml (3 KB at 20.5 KB/sec)
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 3.776 s
[INFO] Finished at: 2015-06-17T09:50:07+01:00
[INFO] Final Memory: 11M/310M
[INFO] ------------------------------------------------------------------------
[ERROR] Plugin org.apache.maven.plugins:maven-dependency-plugin:2.8 or one of its dependencies could not be resolved: Failed to read artifact descriptor for org.apache.maven.plugins:maven-dependency-plugin:jar:2.8: Failure to find org.apache.maven.plugins:maven-plugins:pom:24 in http://localhost:8082/nexus/content/groups/public was cached in the local repository, resolution will not be reattempted until the update interval of nexus has elapsed or updates are forced -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginResolutionException

It has problems resolving dependencies for a number of maven plugins, I have tried looking through the plugin poms and checking to see I have the dependencies in Nexus, but I'm obviously still missing some.

Is there an easy way to see which dependencies it can't resolve?

Here's my settings.xml

<settings>
    <mirrors>
        <mirror> 
            <id>nexus</id>
            <mirrorOf>*</mirrorOf>
            <url>http://localhost:8082/nexus/content/groups/public</url>
        </mirror>
    </mirrors>
    <servers>  
        <server>    
            <id>deployment</id>    
            <username>admin</username>    
            <password>admin123</password>  
        </server>
    </servers>
    <profiles>
       <profile> 
           <id>nexus</id> 
            <repositories>
                <repository>
                    <id>central</id>
                    <url>http://central</url>
                    <releases>
                        <enabled>true</enabled>
                    </releases>
                    <snapshots>
                        <enabled>true</enabled>
                    </snapshots>
                </repository>
            </repositories>
            <pluginRepositories>
                <pluginRepository>
                    <id>central</id>
                    <url>http://central</url>
                    <releases>
                        <enabled>true</enabled>
                    </releases>
                    <snapshots>
                        <enabled>true</enabled>
                    </snapshots>
                </pluginRepository>
            </pluginRepositories>
        </profile> 
    </profiles>
    <activeProfiles> 
        <activeProfile>nexus</activeProfile>
    </activeProfiles>
</settings>

Answer 1

The clue was in the original message

[ERROR] Re-run Maven using the -X switch to enable full debug logging.

So running mvn dependency:resolve -X gave me more specific details

edit: An example of a more specific message it gives

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.708 s
[INFO] Finished at: 2015-06-18T11:15:26+01:00
[INFO] Final Memory: 13M/310M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal on project mavenproject1: Could not resolve dependencies for project com.xxx:mavenproject1:pom:1.0-SNAPSHOT: Could not find artifact org.hamcrest:hamcrest-parent:jar:1.3 in central (https://repo.maven.apache.org/maven2) -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal on project mavenproject1: Could not resolve dependencies for project com.xxx:mavenproject1:pom:1.0-SNAPSHOT: Could not find artifact org.hamcrest:hamcrest-parent:jar:1.3 in central (https://repo.maven.apache.org/maven2)
        at org.apache.maven.lifecycle.internal.LifecycleDependencyResolver.getDependencies(LifecycleDependencyResolver.java:221)
        at org.apache.maven.lifecycle.internal.LifecycleDependencyResolver.resolveProjectDependencies(LifecycleDependencyResolver.java:127)
        at org.apache.maven.lifecycle.internal.MojoExecutor.ensureDependenciesAreResolved(MojoExecutor.java:257)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:200)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
        at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
        at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
        at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
        at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
        at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
        at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
        at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
        at org.apache.maven.cli.MavenCli.execute(MavenCli.java:862)
        at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:286)
        at org.apache.maven.cli.MavenCli.main(MavenCli.java:197)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:606)
        at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
        at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
        at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
        at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: org.apache.maven.project.DependencyResolutionException: Could not resolve dependencies for project com.xxx:mavenproject1:pom:1.0-SNAPSHOT: Could not find artifact org.hamcrest:hamcrest-parent:jar:1.3 in central (https://repo.maven.apache.org/maven2)
        at org.apache.maven.project.DefaultProjectDependenciesResolver.resolve(DefaultProjectDependenciesResolver.java:211)
        at org.apache.maven.lifecycle.internal.LifecycleDependencyResolver.getDependencies(LifecycleDependencyResolver.java:195)
        ... 23 more
Caused by: org.eclipse.aether.resolution.DependencyResolutionException: Could not find artifact org.hamcrest:hamcrest-parent:jar:1.3 in central (https://repo.maven.apache.org/maven2)
        at org.eclipse.aether.internal.impl.DefaultRepositorySystem.resolveDependencies(DefaultRepositorySystem.java:384)
        at org.apache.maven.project.DefaultProjectDependenciesResolver.resolve(DefaultProjectDependenciesResolver.java:205)
        ... 24 more
Caused by: org.eclipse.aether.resolution.ArtifactResolutionException: Could not find artifact org.hamcrest:hamcrest-parent:jar:1.3 in central (https://repo.maven.apache.org/maven2)
        at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolve(DefaultArtifactResolver.java:444)
        at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolveArtifacts(DefaultArtifactResolver.java:246)
        at org.eclipse.aether.internal.impl.DefaultRepositorySystem.resolveDependencies(DefaultRepositorySystem.java:367)
        ... 25 more
Caused by: org.eclipse.aether.transfer.ArtifactNotFoundException: Could not find artifact org.hamcrest:hamcrest-parent:jar:1.3 in central (https://repo.maven.apache.org/maven2)
        at org.eclipse.aether.connector.basic.ArtifactTransportListener.transferFailed(ArtifactTransportListener.java:39)
        at org.eclipse.aether.connector.basic.BasicRepositoryConnector$TaskRunner.run(BasicRepositoryConnector.java:355)
        at org.eclipse.aether.util.concurrency.RunnableErrorForwarder$1.run(RunnableErrorForwarder.java:67)
        at org.eclipse.aether.connector.basic.BasicRepositoryConnector$DirectExecutor.execute(BasicRepositoryConnector.java:581)
        at org.eclipse.aether.connector.basic.BasicRepositoryConnector.get(BasicRepositoryConnector.java:249)
        at org.eclipse.aether.internal.impl.DefaultArtifactResolver.performDownloads(DefaultArtifactResolver.java:520)
        at org.eclipse.aether.internal.impl.DefaultArtifactResolver.resolve(DefaultArtifactResolver.java:421)
        ... 27 more
[ERROR]
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/DependencyResolutionException