android code generation error

Could not resolve all files for configuration ':libraries:opencv:lintClassPath'. > Could not download groovy-all.jar (org.codehaus.groovy:groovy-all:2.4.12) > Could not get resource 'https://jcenter.bintray.com/org/codehaus/groovy/groovy-all/2.4.12/groovy-all-2.4.12.jar'. > Could not GET 'https://jcenter.bintray.com/org/codehaus/groovy/groovy-all/2.4.12/groovy-all-2.4.12.jar'. > sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target