Internal error

FAILURE: Build aborted because of an internal error.
  * What went wrong:
Build aborted because of an unexpected internal error. Please file an issue at: http://forums.gradle.org.
  * Try:
Run with --debug option to get additional debug info.
  * Exception is:
org.gradle.api.UncheckedIOException: java.io.FileNotFoundException: /workspace/phoenix/sw/java/libs/jpixel/bin/doc/swig_ubuntu_install.txt (No such file or directory)
 at org.gradle.util.hash.HashUtil.createHash(HashUtil.java:36)
 at org.gradle.api.internal.changedetection.state.DefaultHasher.hash(DefaultHasher.java:24)
 at org.gradle.api.internal.changedetection.state.CachingHasher.hash(CachingHasher.java:42)
 at org.gradle.api.internal.changedetection.state.DefaultFileSnapshotter.snapshot(DefaultFileSnapshotter.java:44)
 at org.gradle.api.internal.changedetection.state.OutputFilesSnapshotter.snapshot(OutputFilesSnapshotter.java:72)
 at org.gradle.api.internal.changedetection.rules.OutputFilesStateChangeRule.create(OutputFilesStateChangeRule.java:34)
 at org.gradle.api.internal.changedetection.rules.TaskUpToDateState.<init>(TaskUpToDateState.java:47)
 at org.gradle.api.internal.changedetection.changes.DefaultTaskArtifactStateRepository$TaskArtifactStateImpl.getStates(DefaultTaskArtifactStateRepository.java:151)
 at org.gradle.api.internal.changedetection.changes.DefaultTaskArtifactStateRepository$TaskArtifactStateImpl.isUpToDate(DefaultTaskArtifactStateRepository.java:72)
 at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:45)
 at org.gradle.api.internal.tasks.execution.ContextualisingTaskExecuter.execute(ContextualisingTaskExecuter.java:34)
 at org.gradle.api.internal.changedetection.state.CacheLockAcquiringTaskExecuter$1.run(CacheLockAcquiringTaskExecuter.java:39)
 at org.gradle.internal.Factories$1.create(Factories.java:22)
 at org.gradle.cache.internal.DefaultCacheAccess.useCache(DefaultCacheAccess.java:124)
 at org.gradle.cache.internal.DefaultCacheAccess.useCache(DefaultCacheAccess.java:112)
 at org.gradle.cache.internal.DefaultPersistentDirectoryStore.useCache(DefaultPersistentDirectoryStore.java:134)
 at org.gradle.api.internal.changedetection.state.DefaultTaskArtifactStateCacheAccess.useCache(DefaultTaskArtifactStateCacheAccess.java:79)
 at org.gradle.api.internal.changedetection.state.CacheLockAcquiringTaskExecuter.execute(CacheLockAcquiringTaskExecuter.java:37)
 at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:57)
 at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:41)
 at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:51)
 at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:52)
 at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:42)
 at org.gradle.api.internal.AbstractTask.executeWithoutThrowingTaskFailure(AbstractTask.java:282)
 at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.executeTask(DefaultTaskPlanExecutor.java:48)
 at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.processTask(DefaultTaskPlanExecutor.java:34)
 at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.process(DefaultTaskPlanExecutor.java:27)
 at org.gradle.execution.taskgraph.DefaultTaskGraphExecuter.execute(DefaultTaskGraphExecuter.java:89)
 at org.gradle.execution.SelectedTaskExecutionAction.execute(SelectedTaskExecutionAction.java:29)
 at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:61)
 at org.gradle.execution.DefaultBuildExecuter.access$200(DefaultBuildExecuter.java:23)
 at org.gradle.execution.DefaultBuildExecuter$2.proceed(DefaultBuildExecuter.java:67)
 at org.gradle.api.internal.changedetection.state.TaskCacheLockHandlingBuildExecuter$1.run(TaskCacheLockHandlingBuildExecuter.java:31)
 at org.gradle.internal.Factories$1.create(Factories.java:22)
 at org.gradle.cache.internal.DefaultCacheAccess.useCache(DefaultCacheAccess.java:124)
 at org.gradle.cache.internal.DefaultCacheAccess.useCache(DefaultCacheAccess.java:112)
 at org.gradle.cache.internal.DefaultPersistentDirectoryStore.useCache(DefaultPersistentDirectoryStore.java:134)
 at org.gradle.api.internal.changedetection.state.DefaultTaskArtifactStateCacheAccess.useCache(DefaultTaskArtifactStateCacheAccess.java:79)
 at org.gradle.api.internal.changedetection.state.TaskCacheLockHandlingBuildExecuter.execute(TaskCacheLockHandlingBuildExecuter.java:29)
 at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:61)
 at org.gradle.execution.DefaultBuildExecuter.access$200(DefaultBuildExecuter.java:23)
 at org.gradle.execution.DefaultBuildExecuter$2.proceed(DefaultBuildExecuter.java:67)
 at org.gradle.execution.DryRunBuildExecutionAction.execute(DryRunBuildExecutionAction.java:32)
 at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:61)
 at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:54)
 at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:166)
 at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:113)
 at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:81)
 at org.gradle.launcher.exec.InProcessBuildActionExecuter$DefaultBuildController.run(InProcessBuildActionExecuter.java:64)
 at org.gradle.launcher.cli.ExecuteBuildAction.run(ExecuteBuildAction.java:33)
 at org.gradle.launcher.cli.ExecuteBuildAction.run(ExecuteBuildAction.java:24)
 at org.gradle.launcher.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:35)
 at org.gradle.launcher.daemon.server.exec.ExecuteBuild.doBuild(ExecuteBuild.java:45)
 at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:34)
 at org.gradle.launcher.daemon.server.exec.DaemonCommandExecution.proceed(DaemonCommandExecution.java:125)
 at org.gradle.launcher.daemon.server.exec.WatchForDisconnection.execute(WatchForDisconnection.java:42)
 at org.gradle.launcher.daemon.server.exec.DaemonCommandExecution.proceed(DaemonCommandExecution.java:125)
 at org.gradle.launcher.daemon.server.exec.ResetDeprecationLogger.execute(ResetDeprecationLogger.java:24)
 at org.gradle.launcher.daemon.server.exec.DaemonCommandExecution.proceed(DaemonCommandExecution.java:125)
 at org.gradle.launcher.daemon.server.exec.StartStopIfBuildAndStop.execute(StartStopIfBuildAndStop.java:33)
 at org.gradle.launcher.daemon.server.exec.DaemonCommandExecution.proceed(DaemonCommandExecution.java:125)
 at org.gradle.launcher.daemon.server.exec.ReturnResult.execute(ReturnResult.java:34)
 at org.gradle.launcher.daemon.server.exec.DaemonCommandExecution.proceed(DaemonCommandExecution.java:125)
 at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:70)
 at org.gradle.launcher.daemon.server.exec.ForwardClientInput$2.call(ForwardClientInput.java:68)
 at org.gradle.util.Swapper.swap(Swapper.java:38)
 at org.gradle.launcher.daemon.server.exec.ForwardClientInput.execute(ForwardClientInput.java:68)
 at org.gradle.launcher.daemon.server.exec.DaemonCommandExecution.proceed(DaemonCommandExecution.java:125)
 at org.gradle.launcher.daemon.server.exec.LogToClient.doBuild(LogToClient.java:60)
 at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:34)
 at org.gradle.launcher.daemon.server.exec.DaemonCommandExecution.proceed(DaemonCommandExecution.java:125)
 at org.gradle.launcher.daemon.server.exec.EstablishBuildEnvironment.doBuild(EstablishBuildEnvironment.java:59)
 at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:34)
 at org.gradle.launcher.daemon.server.exec.DaemonCommandExecution.proceed(DaemonCommandExecution.java:125)
 at org.gradle.launcher.daemon.server.exec.StartBuildOrRespondWithBusy$1.run(StartBuildOrRespondWithBusy.java:45)
 at org.gradle.launcher.daemon.server.DaemonStateCoordinator.runCommand(DaemonStateCoordinator.java:186)
 at org.gradle.launcher.daemon.server.exec.StartBuildOrRespondWithBusy.doBuild(StartBuildOrRespondWithBusy.java:49)
 at org.gradle.launcher.daemon.server.exec.BuildCommandOnly.execute(BuildCommandOnly.java:34)
 at org.gradle.launcher.daemon.server.exec.DaemonCommandExecution.proceed(DaemonCommandExecution.java:125)
 at org.gradle.launcher.daemon.server.exec.HandleStop.execute(HandleStop.java:36)
 at org.gradle.launcher.daemon.server.exec.DaemonCommandExecution.proceed(DaemonCommandExecution.java:125)
 at org.gradle.launcher.daemon.server.exec.CatchAndForwardDaemonFailure.execute(CatchAndForwardDaemonFailure.java:32)
 at org.gradle.launcher.daemon.server.exec.DaemonCommandExecution.proceed(DaemonCommandExecution.java:125)
 at org.gradle.launcher.daemon.server.exec.DefaultDaemonCommandExecuter.executeCommand(DefaultDaemonCommandExecuter.java:48)
 at org.gradle.launcher.daemon.server.DefaultIncomingConnectionHandler$ConnectionWorker.handleCommand(DefaultIncomingConnectionHandler.java:155)
 at org.gradle.launcher.daemon.server.DefaultIncomingConnectionHandler$ConnectionWorker.receiveAndHandleCommand(DefaultIncomingConnectionHandler.java:128)
 at org.gradle.launcher.daemon.server.DefaultIncomingConnectionHandler$ConnectionWorker.run(DefaultIncomingConnectionHandler.java:116)
 at org.gradle.internal.concurrent.DefaultExecutorFactory$StoppableExecutorImpl$1.run(DefaultExecutorFactory.java:66)
 at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
 at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
 at java.lang.Thread.run(Thread.java:722)
Caused by: java.io.FileNotFoundException: /workspace/phoenix/sw/java/libs/jpixel/bin/doc/swig_ubuntu_install.txt (No such file or directory)
 at java.io.FileInputStream.open(Native Method)
 at java.io.FileInputStream.<init>(FileInputStream.java:138)
 at org.gradle.util.hash.HashUtil.createHash(HashUtil.java:34)
 ... 90 more
    BUILD FAILED

The task it was running is this:

task unpackPixel(type: Copy, dependsOn: checkForPixel) {
    def tarFile = fileTree(projectDir) { include "pixel-*.tar" }
    inputs.files tarFile
    outputs.dir "include"
    outputs.dir "lib"
    from tarTree(resources.gzip(tarFile.singleFile))
    into projectDir
}

Gradle wrapper 1.6, Linux dodev15 3.2.0-34-generic #53-Ubuntu SMP Thu Nov 15 10:48:16 UTC 2012 x86_64 x86_64 x86_64 GNU/Linux

I ran the build a second time, and it worked.