Subsequent builds fail when using a signingConfig

[ChaitanyaPramod]

Gradle step fails when using buck the second time. Deleting .okbuck/keystore makes it work one more time.

Execution failed for task ':app:okbuck'.
> .okbuck/keystore/app/postLollipopDebug.keystore

Our signing config looks like this

    signingConfigs {
        prod {
            storeFile file(prod_keystore) // These values are defined in build.gradle
            storePassword prod_store_password
            keyAlias prod_key_alias
            keyPassword prod_key_password
        }
        debug {
            storeFile file(debug_keystore)
            storePassword debug_store_password
            keyAlias debug_key_alias
            keyPassword debug_key_password
        }
    }

    productFlavors {
        preKitkat {
        }
        postLollipop {
        }
    }

buildTypes {
        prod {
            // ...
            signingConfig signingConfigs.prod
        }

        debug {
            // ...
            signingConfig signingConfigs.debug
        }
    }

This is fairly reproducible in my environment.

EDIT (more notes):
Using okbuck 0.17.1
This happens even when :app:okbuck triggers :okbuckClean and :setupOkbuck
Same thing with app module in okbuck project as well with master (a27f9c7)

[cwoodwar6]

I have the same issue, here is the stacktrace:

Caused by: java.nio.file.FileAlreadyExistsException: .okbuck/keystore/app/debug.keystore
        at sun.nio.fs.UnixCopyFile.copy(UnixCopyFile.java:551)
        at sun.nio.fs.UnixFileSystemProvider.copy(UnixFileSystemProvider.java:253)
        at java.nio.file.Files.copy(Files.java:1274)
        at sun.reflect.GeneratedMethodAccessor3732.invoke(Unknown Source)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
        at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
        at org.codehaus.groovy.runtime.callsite.StaticMetaMethodSite.invoke(StaticMetaMethodSite.java:46)
        at org.codehaus.groovy.runtime.callsite.StaticMetaMethodSite.call(StaticMetaMethodSite.java:91)
        at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:133)
        at com.uber.okbuck.composer.android.KeystoreRuleComposer.compose(KeystoreRuleComposer.groovy:28)
        at com.uber.okbuck.composer.android.KeystoreRuleComposer$compose.call(Unknown Source)
        at com.uber.okbuck.generator.BuckFileGenerator.createRules(BuckFileGenerator.groovy:207)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:93)
        at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:325)
        at org.codehaus.groovy.runtime.metaclass.ClosureMetaClass.invokeMethod(ClosureMetaClass.java:384)
        at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1024)
        at org.codehaus.groovy.runtime.callsite.PogoMetaClassSite.callCurrent(PogoMetaClassSite.java:69)
        at org.codehaus.groovy.runtime.callsite.AbstractCallSite.callCurrent(AbstractCallSite.java:166)
        at com.uber.okbuck.generator.BuckFileGenerator$_createRules_closure1.doCall(BuckFileGenerator.groovy:87)

A temporary workaround is rm -rf .okbuck