我想根据本教程运行基于Kurento（WebRTC MediaServer）的应用程序：http://www.kurento.org/docs/current/tutorials/java/tutorial-1-helloworld.html
运行这些代码之后：
git clone https://github.com/Kurento/kurento-tutorial-java.git
cd kurento-tutorial-java/kurento-hello-world
git checkout 6.1.0
mvn compile exec:java
在最后一行， mvn编译exec：java ，我遇到以下错误：
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building Kurento Java Tutorial 1 - Hello World 6.1.0
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-enforcer-plugin:1.3.1:enforce (enforce-java-version) @ kurento-hello-world ---
[INFO]
[INFO] --- maven-enforcer-plugin:1.3.1:enforce (enforce-maven-version) @ kurento-hello-world ---
[INFO]
[INFO] --- buildnumber-maven-plugin:1.3:create-timestamp (get-build-timestamp) @ kurento-hello-world ---
[INFO]
[INFO] --- buildnumber-maven-plugin:1.3:create (get-scm-revision) @ kurento-hello-world ---
[INFO] Executing: /bin/sh -c cd /home/yashar/kurento-tutorial-java/kurento-hello-world && git rev-parse --verify HEAD
[INFO] Working directory: /home/yashar/kurento-tutorial-java/kurento-hello-world
[INFO] Storing buildNumber: 1202749f372fc2fa0d49ea937a1d58a1a2622622 at timestamp: 1449050266884
[WARNING] Cannot get the branch information from the git repository:
Detecting the current branch failed: fatal: ref HEAD is not a symbolic ref
[INFO] Executing: /bin/sh -c cd /home/yashar/kurento-tutorial-java/kurento-hello-world && git rev-parse --verify HEAD
[INFO] Working directory: /home/yashar/kurento-tutorial-java/kurento-hello-world
[INFO] Storing buildScmBranch: UNKNOWN
[INFO]
[INFO] --- exec-maven-plugin:1.3.2:exec (default) @ kurento-hello-world ---
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1.693s
[INFO] Finished at: Wed Dec 02 10:57:47 CET 2015
[INFO] Final Memory: 13M/303M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.3.2:exec (default) on project kurento-hello-world: Command execution failed. Cannot run program "bower" (in directory "/home/yashar/kurento-tutorial-java/kurento-hello-world"): error=2, No such file or directory -> [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/MojoExecutionException
我想知道问题的根源以及如何解决问题。谢谢