openconfig-bgp.yang fails with:

[ERROR] yang-to-sources: Unable to generate sources with org.opendaylight.yangtools.maven.sal.api.gen.plugin.CodeGeneratorImpl generator
java.lang.IllegalArgumentException: Failed to find leafref target: ../config/neighbor-address
at org.opendaylight.yangtools.sal.binding.yang.types.TypeProviderImpl.provideTypeForLeafref(TypeProviderImpl.java:503)
at org.opendaylight.yangtools.sal.binding.yang.types.TypeProviderImpl.javaTypeForLeafrefOrIdentityRef(TypeProviderImpl.java:304)
at org.opendaylight.yangtools.sal.binding.yang.types.TypeProviderImpl.javaTypeForSchemaDefinitionType(TypeProviderImpl.java:217)
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.resolveLeafSchemaNodeAsMethod(BindingGeneratorImpl.java:1384)
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.addSchemaNodeToListBuilders(BindingGeneratorImpl.java:1840)
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.listToGenType(BindingGeneratorImpl.java:352)
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.addSchemaNodeToBuilderAsMethod(BindingGeneratorImpl.java:1118)
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.resolveDataSchemaNodes(BindingGeneratorImpl.java:1049)
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.groupingToGenType(BindingGeneratorImpl.java:697)
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.groupingsToGenTypes(BindingGeneratorImpl.java:675)
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.moduleToGenTypes(BindingGeneratorImpl.java:258)
at org.opendaylight.yangtools.sal.binding.generator.impl.BindingGeneratorImpl.generateTypes(BindingGeneratorImpl.java:236)
at org.opendaylight.yangtools.maven.sal.api.gen.plugin.CodeGeneratorImpl.generateSources(CodeGeneratorImpl.java:61)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.generateSourcesWithOneGenerator(YangToSourcesProcessor.java:330)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.generateSources(YangToSourcesProcessor.java:275)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.execute(YangToSourcesProcessor.java:95)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesMojo.execute(YangToSourcesMojo.java:116)
at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:132)
at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
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:120)
at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:355)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:155)
at org.apache.maven.cli.MavenCli.execute(MavenCli.java:584)
at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:216)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:160)
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:497)
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)

Which does not point to the source of the problem (statement).