このエラーメッセージに関する原因と対処に関して説明します。
エラーメッセージ(英語)：
sdk hostname cannot be null
対処
関連リンク
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aws/aws-sdk-java - GitHub
https://github.com/aws/aws-sdk-java/blob/master/aws-java-sdk-core/src/main/java/com/amazonaws/util/A・・・
AwsHostNameUtils (AWS SDK for Java - 1.11.500)
https://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/com/amazonaws/util/AwsHostNameUtils.html
EC2MetadataUtils (AWS SDK for Java - 1.11.505) - AWS Documentation
https://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/com/amazonaws/util/EC2MetadataUtils.html
Serialized Form (AWS SDK for Java - 1.11.500) - AWS Documentation
https://docs.aws.amazon.com/AWSJavaSDK/latest/javadoc/serialized-form.html
#10432 (Missing session token when making the ... - Cyberduck
https://trac.cyberduck.io/ticket/10432