Prevent the accidental use of Flyway's StringUtils

See gh-11396

spring-boot-parent/src/checkstyle/checkstyle.xml

@@ -73,7 +73,7 @@
 				value="org.assertj.core.api.Assertions.*, org.junit.Assert.*, org.junit.Assume.*, org.junit.internal.matchers.ThrowableMessageMatcher.*, org.hamcrest.CoreMatchers.*, org.hamcrest.Matchers.*, org.springframework.boot.configurationprocessor.ConfigurationMetadataMatchers.*, org.springframework.boot.configurationprocessor.TestCompiler.*, org.springframework.boot.test.autoconfigure.AutoConfigurationImportedCondition.*, org.mockito.Mockito.*, org.mockito.BDDMockito.*, org.mockito.Matchers.*, org.springframework.restdocs.mockmvc.MockMvcRestDocumentation.*, org.springframework.restdocs.hypermedia.HypermediaDocumentation.*, org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*, org.springframework.test.web.servlet.result.MockMvcResultMatchers.*, org.springframework.security.test.web.servlet.request.SecurityMockMvcRequestPostProcessors.*, org.springframework.security.test.web.servlet.setup.SecurityMockMvcConfigurers.*, org.springframework.hateoas.mvc.ControllerLinkBuilder.linkTo, org.springframework.test.web.client.match.MockRestRequestMatchers.*, org.springframework.test.web.client.response.MockRestResponseCreators.*" />
 		</module>
 		<module name="com.puppycrawl.tools.checkstyle.checks.imports.IllegalImportCheck">
-			<property name="illegalPkgs" value="sun, org.apache.commons.(?!codec|dbcp|dbcp2|logging|pool|pool2).*, com.google.common.(?!cache).*"/>
+			<property name="illegalPkgs" value="sun, org.apache.commons.(?!codec|dbcp|dbcp2|logging|pool|pool2).*, com.google.common.(?!cache).*, org.flywaydb.core.internal"/>
 			<property name="regexp" value="true"/>
 		</module>
 		<module name="com.puppycrawl.tools.checkstyle.checks.imports.RedundantImportCheck" />