Unable t generate yang files

[ERROR] Failed to execute goal org.opendaylight.yangtools:yang-maven-plugin:0.5.9-SNAPSHOT:generate-sources (default) on project pcep-api: yang-to-sources: One or more code generators failed, including failed list(generatorClass=exception)

{org.opendaylight.yangtools.yang.unified.doc.generator.maven.DocumentationGeneratorImpl=java.lang.NullPointerException}

-> [Help 1]

[ERROR] yang-to-sources: Unable to generate sources with org.opendaylight.yangtools.yang.unified.doc.generator.maven.DocumentationGeneratorImpl generator
java.lang.NullPointerException
at org.opendaylight.yangtools.yang.unified.doc.generator.GeneratorImpl.schemaPathAsRestconfPath(GeneratorImpl.java:1383)
at org.opendaylight.yangtools.yang.unified.doc.generator.GeneratorImpl.augmentations(GeneratorImpl.java:396)
at org.opendaylight.yangtools.yang.unified.doc.generator.GeneratorImpl.body(GeneratorImpl.java:200)
at org.opendaylight.yangtools.yang.unified.doc.generator.GeneratorImpl.generate(GeneratorImpl.java:159)
at org.opendaylight.yangtools.yang.unified.doc.generator.GeneratorImpl.generateDocumentation(GeneratorImpl.java:121)
at org.opendaylight.yangtools.yang.unified.doc.generator.GeneratorImpl.generate(GeneratorImpl.java:101)
at org.opendaylight.yangtools.yang.unified.doc.generator.maven.DocumentationGeneratorImpl.generateSources(DocumentationGeneratorImpl.java:22)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.generateSourcesWithOneGenerator(YangToSourcesProcessor.java:276)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.generateSources(YangToSourcesProcessor.java:221)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.execute(YangToSourcesProcessor.java:87)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesMojo.execute(YangToSourcesMojo.java:107)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:101)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:209)
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:84)
at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:59)
at org.apache.maven.lifecycle.internal.LifecycleStarter.singleThreadedBuild(LifecycleStarter.java:183)
at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:161)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:322)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:158)
at org.apache.maven.cli.MavenCli.execute(MavenCli.java:537)
at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:196)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:141)
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:601)
at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:290)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:230)
at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:409)
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:352)