Github user zentol commented on the issue:
https://github.com/apache/flink/pull/5059
Does this remove all checkstyle violations in core.fs? If so, please remove
the exlcusion in `/tools/maven/suppressions-core.xml`.
```
<suppress
files="(.*)core[/\\]fs[/\\](.*)"
checks="NewlineAtEndOfFile|RegexpSingleline|TodoComment|RedundantImport|ImportOrder|RedundantModifier|JavadocMethod|JavadocParagraph|JavadocType|JavadocStyle|PackageName|TypeNameCheck|ConstantNameCheck|StaticVariableNameCheck|MemberNameCheck|MethodNameCheck|ParameterName|LocalFinalVariableName|LocalVariableName|LeftCurly|UpperEll|FallThrough|reliefPattern|SimplifyBooleanExpression|EmptyStatement|ModifierOrder|EmptyLineSeparator|WhitespaceAround|WhitespaceAfter|NoWhitespaceAfter|NoWhitespaceBefore|OperatorWrap|ParenPad"/>
<!--Only additional checks for test sources. Those checks were present
in the "pre-strict" checkstyle but were not applied to test sources. We do not
want to suppress them for sources directory-->
<suppress
files="(.*)test[/\\](.*)core[/\\]fs[/\\](.*)"
checks="AvoidStarImport"/>
```
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