I am trying to release my Android application with Gradle.

Everything works, including the `./gradlew clean build assembleRelease` command.

However, as soon as I try to use proguard, Gradle fail to build the release version.

Here is the error I get (stack trace activated):

```
...
:OSkin:validateDebugSigning
:OSkin:packageDebug
:OSkin:assembleDebug
:OSkin:prepareReleaseDependencies
:OSkin:compileReleaseAidl
:OSkin:generateReleaseBuildConfig
:OSkin:mergeReleaseAssets
:OSkin:compileReleaseRenderscript
:OSkin:mergeReleaseResources
:OSkin:processReleaseManifest
:OSkin:processReleaseResources
:OSkin:compileRelease UP-TO-DATE
:OSkin:proguardRelease
ProGuard, version 4.9
Reading input...
Reading program directory [/home/geantvert/workspace/OSkinProject/OSkin/build/classes/release]
:OSkin:proguardRelease FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':OSkin:proguardRelease'.
> Can't read [/home/geantvert/workspace/OSkinProject/OSkin/build/classes/release] (No such file or directory)

* Try:
Run with --info or --debug option to get more log output.

* Exception is:
org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':OSkin:proguardRelease'.
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:69)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.execute(ExecuteActionsTaskExecuter.java:46)
    at org.gradle.api.internal.tasks.execution.PostExecutionAnalysisTaskExecuter.execute(PostExecutionAnalysisTaskExecuter.java:35)
    at org.gradle.api.internal.tasks.execution.SkipUpToDateTaskExecuter.execute(SkipUpToDateTaskExecuter.java:62)
    at org.gradle.api.internal.tasks.execution.ValidatingTaskExecuter.execute(ValidatingTaskExecuter.java:58)
    at org.gradle.api.internal.tasks.execution.SkipEmptySourceFilesTaskExecuter.execute(SkipEmptySourceFilesTaskExecuter.java:42)
    at org.gradle.api.internal.tasks.execution.SkipTaskWithNoActionsExecuter.execute(SkipTaskWithNoActionsExecuter.java:52)
    at org.gradle.api.internal.tasks.execution.SkipOnlyIfTaskExecuter.execute(SkipOnlyIfTaskExecuter.java:53)
    at org.gradle.api.internal.tasks.execution.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:43)
    at org.gradle.api.internal.AbstractTask.executeWithoutThrowingTaskFailure(AbstractTask.java:286)
    at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.executeTask(AbstractTaskPlanExecutor.java:80)
    at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.processTask(AbstractTaskPlanExecutor.java:66)
    at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.executeTaskWithCacheLock(AbstractTaskPlanExecutor.java:58)
    at org.gradle.execution.taskgraph.AbstractTaskPlanExecutor$TaskExecutorWorker.run(AbstractTaskPlanExecutor.java:47)
    at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor$1.run(DefaultTaskPlanExecutor.java:33)
    at org.gradle.internal.Factories$1.create(Factories.java:22)
    at org.gradle.cache.internal.DefaultCacheAccess.longRunningOperation(DefaultCacheAccess.java:214)
    at org.gradle.cache.internal.DefaultCacheAccess.longRunningOperation(DefaultCacheAccess.java:276)
    at org.gradle.cache.internal.DefaultPersistentDirectoryStore.longRunningOperation(DefaultPersistentDirectoryStore.java:142)
    at org.gradle.api.internal.changedetection.state.DefaultTaskArtifactStateCacheAccess.longRunningOperation(DefaultTaskArtifactStateCacheAccess.java:78)
    at org.gradle.execution.taskgraph.DefaultTaskPlanExecutor.process(DefaultTaskPlanExecutor.java:31)
    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$2.proceed(DefaultBuildExecuter.java:67)
    at org.gradle.execution.DryRunBuildExecutionAction.execute(DryRunBuildExecutionAction.java:32)
    at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:61)
    at org.gradle.execution.DefaultBuildExecuter.execute(DefaultBuildExecuter.java:54)
    at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:166)
    at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:113)
    at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:81)
    at org.gradle.launcher.exec.InProcessBuildActionExecuter$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.exec.InProcessBuildActionExecuter.execute(InProcessBuildActionExecuter.java:26)
    at org.gradle.launcher.cli.RunBuildAction.run(RunBuildAction.java:50)
    at org.gradle.api.internal.Actions$RunnableActionAdapter.execute(Actions.java:171)
    at org.gradle.launcher.cli.CommandLineActionFactory$ParseAndBuildAction.execute(CommandLineActionFactory.java:201)
    at org.gradle.launcher.cli.CommandLineActionFactory$ParseAndBuildAction.execute(CommandLineActionFactory.java:174)
    at org.gradle.launcher.cli.CommandLineActionFactory$WithLogging.execute(CommandLineActionFactory.java:170)
    at org.gradle.launcher.cli.CommandLineActionFactory$WithLogging.execute(CommandLineActionFactory.java:139)
    at org.gradle.launcher.cli.ExceptionReportingAction.execute(ExceptionReportingAction.java:33)
    at org.gradle.launcher.cli.ExceptionReportingAction.execute(ExceptionReportingAction.java:22)
    at org.gradle.launcher.Main.doAction(Main.java:48)
    at org.gradle.launcher.bootstrap.EntryPoint.run(EntryPoint.java:45)
    at org.gradle.launcher.Main.main(Main.java:39)
    at org.gradle.launcher.bootstrap.ProcessBootstrap.runNoExit(ProcessBootstrap.java:50)
    at org.gradle.launcher.bootstrap.ProcessBootstrap.run(ProcessBootstrap.java:32)
    at org.gradle.launcher.GradleMain.main(GradleMain.java:26)
    at org.gradle.wrapper.BootstrapMainStarter.start(BootstrapMainStarter.java:33)
    at org.gradle.wrapper.WrapperExecutor.execute(WrapperExecutor.java:130)
    at org.gradle.wrapper.GradleWrapperMain.main(GradleWrapperMain.java:48)
Caused by: java.io.IOException: Can't read [/home/geantvert/workspace/OSkinProject/OSkin/build/classes/release] (No such file or directory)
    at proguard.InputReader.readInput(InputReader.java:230)
    at proguard.InputReader.readInput(InputReader.java:200)
    at proguard.InputReader.readInput(InputReader.java:178)
    at proguard.InputReader.execute(InputReader.java:78)
    at proguard.ProGuard.readInput(ProGuard.java:197)
    at proguard.ProGuard.execute(ProGuard.java:79)
    at proguard.gradle.ProGuardTask.proguard(ProGuardTask.java:958)
    at org.gradle.api.internal.BeanDynamicObject$MetaClassAdapter.invokeMethod(BeanDynamicObject.java:248)
    at org.gradle.api.internal.BeanDynamicObject.invokeMethod(BeanDynamicObject.java:136)
    at org.gradle.api.internal.CompositeDynamicObject.invokeMethod(CompositeDynamicObject.java:147)
    at proguard.gradle.ProGuardTask_Decorated.invokeMethod(Unknown Source)
    at org.gradle.api.internal.BeanDynamicObject$MetaClassAdapter.invokeMethod(BeanDynamicObject.java:248)
    at org.gradle.api.internal.BeanDynamicObject.invokeMethod(BeanDynamicObject.java:136)
    at org.gradle.api.internal.CompositeDynamicObject.invokeMethod(CompositeDynamicObject.java:147)
    at proguard.gradle.ProGuardTask_Decorated.invokeMethod(Unknown Source)
    at org.gradle.util.ReflectionUtil.invoke(ReflectionUtil.groovy:23)
    at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.doExecute(AnnotationProcessingTaskFactory.java:220)
    at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:213)
    at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$StandardTaskAction.execute(AnnotationProcessingTaskFactory.java:202)
    at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:530)
    at org.gradle.api.internal.AbstractTask$TaskActionWrapper.execute(AbstractTask.java:513)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeAction(ExecuteActionsTaskExecuter.java:80)
    at org.gradle.api.internal.tasks.execution.ExecuteActionsTaskExecuter.executeActions(ExecuteActionsTaskExecuter.java:61)
    ... 53 more
Caused by: java.io.IOException: No such file or directory
    at proguard.io.DirectoryPump.pumpDataEntries(DirectoryPump.java:50)
    at proguard.InputReader.readInput(InputReader.java:226)
    ... 75 more

BUILD FAILED

Total time: 42.363 secs

```

Here is my gradle file:

```
buildscript {
    repositories {
        mavenCentral()

    }
    dependencies {
        classpath 'com.android.tools.build:gradle:0.5.+'
    }
}
apply plugin: 'android'

repositories {
    mavenCentral()
    maven {
        url 'http://www.bugsense.com/gradle/'
    }
}

dependencies {
    compile fileTree(dir: 'libs', include: '*.jar')

    compile 'com.google.guava:guava:14.+'
    compile 'com.google.code.gson:gson:2.+'
    compile 'org.zeroturnaround:zt-zip:1.+'
    compile 'com.github.japgolly.android:svg-android:2.+'
    compile('de.keyboardsurfer.android.widget:crouton:1.8.1') {
        exclude module: 'support-v4'
        compile 'com.android.support:support-v4:18.+'
    }
    compile 'com.squareup:otto:1.3.4'
    compile 'com.squareup.okhttp:okhttp:1.2.+'
    compile 'com.squareup.picasso:picasso:1+'
    compile 'com.bugsense.trace:bugsense:3.5'

    //Google Drive SDK
    compile 'com.google.android.gms:play-services:3.+'
    compile 'com.google.apis:google-api-services-drive:v2+'

    compile('com.google.api-client:google-api-client:1.+') {
        exclude(group: 'xpp3', module: 'xpp3')
        exclude(group: 'org.apache.httpcomponents', module: 'httpclient')
        exclude(group: 'junit', module: 'junit')
        exclude(group: 'com.google.android', module: 'android')
    }
    compile('com.google.api-client:google-api-client-android:1.+') {
        exclude group: 'xpp3'
        exclude group: 'com.google.android.google-play-services'
    }
    compile('com.google.http-client:google-http-client-jackson:1.+') {
        exclude group: 'xpp3'
    }
    compile('com.google.http-client:google-http-client-gson:1.+') {
        exclude group: 'xpp3'
    }

    compile 'com.google.apis:google-api-services-plus:v1+'

    compile 'com.netflix.rxjava:rxjava-android:+'

    compile('com.github.frankiesardo:icepick:2+') {
        exclude module: 'support-v4'
        compile 'com.android.support:support-v4:18.+'
    }

//    compile (group: 'com.google.apis', name: 'google-api-services-youtube', version: 'v3-rev56-1.15.0-rc')
}

android {
    compileSdkVersion 18
    buildToolsVersion "18.0.1"

    defaultConfig {
        minSdkVersion 14
        targetSdkVersion 18
    }
    signingConfigs {
        release {
                    storeFile file('path_to_file')
                    storePassword '***'
                    keyAlias '***'
                    keyPassword '***'
                }
    }

    buildTypes
            {
                release {
                    runProguard true
                    proguardFile getDefaultProguardFile('proguard-android.txt')
                    proguardFile 'proguard-project.txt'
                    signingConfig signingConfigs.release 
               }
            }
}

```

Does anyone has an idea of what is the issue?

Regards

Edit: `./gradlew clean assembleDebug` works perfectly! and `./gradlew clean build assembleRelease` works if runProguard is set to off. So it's a 100% proGuard issue.