Promote syntactic errors from WARNING to ERROR

If the following (or similar) warning is encountered:

[WARNING] line 300:1 mismatched input '}' expecting

{'when', 'uses', 'status', 'reference', 'list', 'leaf-list', 'leaf', 'if-feature', 'description', 'container', 'choice', 'case', 'anyxml', IDENTIFIER}

the tools continue with:

[WARNING] Import:bgp-message:default by module:bgp-linkstate:2013-09-18 does not specify revision, using:bgp-message:2013-09-18 for module dependency sort
[WARNING] Import:bgp-multiprotocol:default by module:bgp-linkstate:2013-09-18 does not specify revision, using:bgp-multiprotocol:2013-09-18 for module dependency sort
[WARNING] Import:bgp-linkstate:default by module:bgpls-nlri:2013-08-12 does not specify revision, using:bgp-linkstate:2013-09-18 for module dependency sort
[WARNING] Import:bgp-types:default by module:bgp-message:2013-09-18 does not specify revision, using:bgp-types:2013-09-19 for module dependency sort
[WARNING] Import:bgp-message:default by module:bgp-multiprotocol:2013-09-18 does not specify revision, using:bgp-message:2013-09-18 for module dependency sort
[WARNING] Import:bgp-types:default by module:bgp-multiprotocol:2013-09-18 does not specify revision, using:bgp-types:2013-09-19 for module dependency sort
[ERROR] yang-to-sources: Unable to parse yang files from /home/nite/bgpcep/bgp/parser-api/src/main/yang
org.opendaylight.yangtools.yang.parser.util.YangParseException: Error in module 'bgpls-nlri' at line 117: Referenced grouping 'igp-bits' not found.
at org.opendaylight.yangtools.yang.parser.util.GroupingUtils.getTargetGroupingFromModules(GroupingUtils.java:119)
at org.opendaylight.yangtools.yang.parser.impl.YangParserImpl.resolveUsesTargetGrouping(YangParserImpl.java:779)
at org.opendaylight.yangtools.yang.parser.impl.YangParserImpl.build(YangParserImpl.java:305)
at org.opendaylight.yangtools.yang.parser.impl.YangParserImpl.parseYangModelsFromStreamsMapped(YangParserImpl.java:201)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.processYang(YangToSourcesProcessor.java:97)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesProcessor.execute(YangToSourcesProcessor.java:74)
at org.opendaylight.yangtools.yang2sources.plugin.YangToSourcesMojo.execute(YangToSourcesMojo.java:102)
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:320)
at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:156)
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:606)
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)

E.g. leading the user to a completely different territory. What should have happened is that processing should have stopped at the syntactic error and no other messages should've been reported.