'' mit Prefix '' error: System.ArgumentException: Key is a required property and must be set before making this call.
Parameter name: GetObjectMetadataRequest.Key
   at Amazon.S3.Model.Internal.MarshallTransformations.GetObjectMetadataRequestMarshaller.Marshall(GetObjectMetadataRequest headObjectRequest)
   at Amazon.Runtime.Internal.Marshaller.PreInvoke(IExecutionContext executionContext) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Pipeline\Handlers\Marshaller.cs:line 79
   at Amazon.Runtime.Internal.Marshaller.InvokeSync(IExecutionContext executionContext) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Pipeline\Handlers\Marshaller.cs:line 37
   at Amazon.Runtime.Internal.CallbackHandler.InvokeSync(IExecutionContext executionContext) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Pipeline\Handlers\CallbackHandler.cs:line 46
   at Amazon.S3.Internal.AmazonS3ExceptionHandler.InvokeSync(IExecutionContext executionContext)
   at Amazon.Runtime.Internal.ErrorCallbackHandler.InvokeSync(IExecutionContext executionContext) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Pipeline\Handlers\ErrorCallbackHandler.cs:line 44
   at Amazon.Runtime.Internal.MetricsHandler.InvokeSync(IExecutionContext executionContext) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Pipeline\Handlers\MetricsHandler.cs:line 40
   at Amazon.Runtime.Internal.RuntimePipeline.InvokeSync(IExecutionContext executionContext) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\Pipeline\RuntimePipeline.cs:line 136
   at Amazon.Runtime.AmazonServiceClient.Invoke[TResponse](AmazonWebServiceRequest request, InvokeOptionsBase options) in D:\JenkinsWorkspaces\trebuchet-stage-release\AWSDotNetPublic\sdk\src\Core\Amazon.Runtime\AmazonServiceClient.cs:line 206
   at AWSFuncs.DoesFileExist(String BucketName, String Key, String Prefix, BasicAWSCredentials credentials)
   at Newsletter.Page_Load(Object Src, EventArgs E)