Failed to execute goal de.saumya.mojo:gem-maven-plugin:1.1.5:exec (default) on project referenceapplication-omod

I am trying to build RefApp 2.5 but i get following error in eclipse and cmd. java version 1.8.0_121 Apache Maven 3.3.9 (bb52d8502b132ec0a5a3f4c09453c07478323dc5; 2015-11-10T21:11:47+04:30)

[INFO] ------------------------------------------------------------------------
[INFO] Building Reference Application Module OMOD 2.5
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-clean-plugin:2.5:clean (default-clean) @ referenceapplication-omod ---
[INFO] Deleting C:\Users\Pardess\workspace\openmrs-module-referenceapplication-2.5\omod\target
[INFO]
[INFO] --- maven-openmrs-plugin:1.0.1:initialize-module (init) @ referenceapplication-omod ---
[INFO]
[INFO] --- maven-dependency-plugin:2.4:unpack-dependencies (Expand moduleApplicationContext and messages) @ referenceapplication-omod ---
[INFO] Unpacking C:\Users\Pardess\workspace\openmrs-module-referenceapplication-2.5\api\target\referenceapplication-api-2.5.jar to C:\Users\Pardess\workspace\openmrs-module-referenceapplication-2.5\omod\target\classes with includes "**/*" and excludes ""
[INFO]
[INFO] --- maven-dependency-plugin:2.4:unpack (Fetch SASS sources from uicommons) @ referenceapplication-omod ---
[INFO] Configured Artifact: org.openmrs.module:uicommons-scss:?:zip
[INFO] Unpacking C:\Users\Pardess\.m2\repository\org\openmrs\module\uicommons-scss\2.1\uicommons-scss-2.1.zip to C:\Users\Pardess\workspace\openmrs-module-referenceapplication-2.5\omod\src\main\compass\sass-external with includes "" and excludes ""
[INFO]
[INFO] --- gem-maven-plugin:1.1.5:exec (default) @ referenceapplication-omod ---
[WARNING] Error injecting: de.saumya.mojo.gem.ExecMojo
java.lang.TypeNotPresentException: Type de.saumya.mojo.gem.ExecMojo not present
        at org.eclipse.sisu.space.URLClassSpace.loadClass(URLClassSpace.java:143)
        at org.eclipse.sisu.space.NamedClass.load(NamedClass.java:46)
        at org.eclipse.sisu.space.AbstractDeferredClass.get(AbstractDeferredClass.java:48)
        at com.google.inject.internal.ProviderInternalFactory.provision(ProviderInternalFactory.java:81)
        at com.google.inject.internal.InternalFactoryToInitializableAdapter.provision(InternalFactoryToInitializableAdapter.java:53)
        at com.google.inject.internal.ProviderInternalFactory$1.call(ProviderInternalFactory.java:65)
        at com.google.inject.internal.ProvisionListenerStackCallback$Provision.provision(ProvisionListenerStackCallback.java:115)
        at org.eclipse.sisu.bean.BeanScheduler$Activator.onProvision(BeanScheduler.java:176)
        at com.google.inject.internal.ProvisionListenerStackCallback$Provision.provision(ProvisionListenerStackCallback.java:126)
        at com.google.inject.internal.ProvisionListenerStackCallback.provision(ProvisionListenerStackCallback.java:68)
        at com.google.inject.internal.ProviderInternalFactory.circularGet(ProviderInternalFactory.java:63)
        at com.google.inject.internal.InternalFactoryToInitializableAdapter.get(InternalFactoryToInitializableAdapter.java:45)
        at com.google.inject.internal.InjectorImpl$2$1.call(InjectorImpl.java:1016)
        at com.google.inject.internal.InjectorImpl.callInContext(InjectorImpl.java:1092)
        at com.google.inject.internal.InjectorImpl$2.get(InjectorImpl.java:1012)
        at org.eclipse.sisu.inject.Guice4$1.get(Guice4.java:162)
        at org.eclipse.sisu.inject.LazyBeanEntry.getValue(LazyBeanEntry.java:81)
        at org.eclipse.sisu.plexus.LazyPlexusBean.getValue(LazyPlexusBean.java:51)
        at org.codehaus.plexus.DefaultPlexusContainer.lookup(DefaultPlexusContainer.java:263)
        at org.codehaus.plexus.DefaultPlexusContainer.lookup(DefaultPlexusContainer.java:255)
        at org.apache.maven.plugin.internal.DefaultMavenPluginManager.getConfiguredMojo(DefaultMavenPluginManager.java:517)
        at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:121)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
        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:863)
        at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
        at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        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: java.lang.ClassNotFoundException: de.saumya.mojo.gem.ExecMojo
        at org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy.loadClass(SelfFirstStrategy.java:50)
        at org.codehaus.plexus.classworlds.realm.ClassRealm.unsynchronizedLoadClass(ClassRealm.java:271)
        at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:247)
        at org.codehaus.plexus.classworlds.realm.ClassRealm.loadClass(ClassRealm.java:239)
        at org.eclipse.sisu.space.URLClassSpace.loadClass(URLClassSpace.java:139)
        ... 42 more
[INFO] ------------------------------------------------------------------------
[INFO] Reactor Summary:
[INFO]
[INFO] Reference Application Module ....................... SUCCESS [  0.229 s]
[INFO] Reference Application Module API ................... SUCCESS [ 35.361 s]
[INFO] Reference Application Module OMOD .................. FAILURE [  1.171 s]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 37.773 s
[INFO] Finished at: 2017-03-31T12:05:14+04:30
[INFO] Final Memory: 52M/496M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal de.saumya.mojo:gem-maven-plugin:1.1.5:exec (default) on project referenceapplication-omod: Execution default of goal de.saumya.mojo:gem-maven-plugin:1.1.5:exec failed: Unable to load the mojo 'exec' in the plugin 'de.saumya.mojo:gem-maven-plugin:1.1.5'. A required class is missing: de.saumya.mojo.gem.ExecMojo
[ERROR] -----------------------------------------------------
[ERROR] realm =    extension>de.saumya.mojo:gem-maven-plugin:1.1.5
[ERROR] strategy = org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy
[ERROR] urls[0] = file:/C:/Users/Pardess/.m2/repository/de/saumya/mojo/gem-maven-plugin/1.1.5/gem-maven-plugin-1.1.5.jar
[ERROR] urls[1] = file:/C:/Users/Pardess/.m2/repository/de/saumya/mojo/jruby-maven-plugin/1.1.5/jruby-maven-plugin-1.1.5.jar
[ERROR] urls[2] = file:/C:/Users/Pardess/.m2/repository/de/saumya/mojo/ruby-tools/1.1.5/ruby-tools-1.1.5.jar
[ERROR] urls[3] = file:/C:/Users/Pardess/.m2/repository/org/apache/ant/ant/1.9.4/ant-1.9.4.jar
[ERROR] urls[4] = file:/C:/Users/Pardess/.m2/repository/org/apache/ant/ant-launcher/1.9.4/ant-launcher-1.9.4.jar
[ERROR] urls[5] = file:/C:/Users/Pardess/.m2/repository/org/codehaus/plexus/plexus-archiver/3.0/plexus-archiver-3.0.jar
[ERROR] urls[6] = file:/C:/Users/Pardess/.m2/repository/org/codehaus/plexus/plexus-io/2.4.1/plexus-io-2.4.1.jar
[ERROR] urls[7] = file:/C:/Users/Pardess/.m2/repository/commons-io/commons-io/2.2/commons-io-2.2.jar
[ERROR] urls[8] = file:/C:/Users/Pardess/.m2/repository/org/apache/commons/commons-compress/1.9/commons-compress-1.9.jar
[ERROR] urls[9] = file:/C:/Users/Pardess/.m2/repository/org/xerial/snappy/snappy-java/1.1.1.6/snappy-java-1.1.1.6.jar
[ERROR] urls[10] = file:/C:/Users/Pardess/.m2/repository/org/sonatype/plexus/plexus-build-api/0.0.7/plexus-build-api-0.0.7.jar
[ERROR] urls[11] = file:/C:/Users/Pardess/.m2/repository/org/sonatype/sisu/sisu-inject-bean/2.1.1/sisu-inject-bean-2.1.1.jar
[ERROR] urls[12] = file:/C:/Users/Pardess/.m2/repository/org/sonatype/sisu/sisu-guice/2.9.4/sisu-guice-2.9.4-no_aop.jar
[ERROR] urls[13] = file:/C:/Users/Pardess/.m2/repository/org/sonatype/aether/aether-util/1.11/aether-util-1.11.jar
[ERROR] urls[14] = file:/C:/Users/Pardess/.m2/repository/org/codehaus/plexus/plexus-interpolation/1.14/plexus-interpolation-1.14.jar
[ERROR] urls[15] = file:/C:/Users/Pardess/.m2/repository/org/codehaus/plexus/plexus-utils/2.0.6/plexus-utils-2.0.6.jar
[ERROR] urls[16] = file:/C:/Users/Pardess/.m2/repository/org/codehaus/plexus/plexus-component-annotations/1.5.5/plexus-component-annotations-1.5.5.jar
[ERROR] urls[17] = file:/C:/Users/Pardess/.m2/repository/org/sonatype/plexus/plexus-sec-dispatcher/1.3/plexus-sec-dispatcher-1.3.jar
[ERROR] urls[18] = file:/C:/Users/Pardess/.m2/repository/org/sonatype/plexus/plexus-cipher/1.4/plexus-cipher-1.4.jar
[ERROR] Number of foreign imports: 1
[ERROR] import: Entry[import  from realm ClassRealm[maven.api, parent: null]]
[ERROR]
[ERROR] -----------------------------------------------------
[ERROR] -> [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/PluginContainerException
[ERROR]
[ERROR] After correcting the problems, you can resume the build with the command
[ERROR]   mvn  -rf :referenceapplication-omod

if i remove the following plugin then it is compiled successfully but css files are missing.

@dkayiwa , @darius