Certificate required

I'm trying to run server but faced with weird issue:

``

[debug] sbt-js template properties {}
javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid ce
rtification path to requested target
at sun.security.ssl.Alerts.getSSLException(Alerts.java:192)

Caused by: sun.security.validator.ValidatorException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to reques
ted target
at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:387)
at sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:292)
at sun.security.validator.Validator.validate(Validator.java:260)
at sun.security.ssl.X509TrustManagerImpl.validate(X509TrustManagerImpl.java:324)
at sun.security.ssl.X509TrustManagerImpl.checkTrusted(X509TrustManagerImpl.java:229)
at sun.security.ssl.X509TrustManagerImpl.checkServerTrusted(X509TrustManagerImpl.java:124)
at sun.security.ssl.ClientHandshaker.serverCertificate(ClientHandshaker.java:1479)
at sun.security.ssl.ClientHandshaker.processMessage(ClientHandshaker.java:212)
at sun.security.ssl.Handshaker.processLoop(Handshaker.java:979)
at sun.security.ssl.Handshaker.process_record(Handshaker.java:914)
at sun.security.ssl.SSLSocketImpl.readRecord(SSLSocketImpl.java:1062)
at sun.security.ssl.SSLSocketImpl.performInitialHandshake(SSLSocketImpl.java:1375)
at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1403)
at sun.security.ssl.SSLSocketImpl.startHandshake(SSLSocketImpl.java:1387)
at sun.net.www.protocol.https.HttpsClient.afterConnect(HttpsClient.java:563)
at sun.net.www.protocol.https.AbstractDelegateHttpsURLConnection.connect(AbstractDelegateHttpsURLConnection.java:185)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream0(HttpURLConnection.java:1512)
at sun.net.www.protocol.http.HttpURLConnection.access$200(HttpURLConnection.java:90)
at sun.net.www.protocol.http.HttpURLConnection$9.run(HttpURLConnection.java:1432)
at sun.net.www.protocol.http.HttpURLConnection$9.run(HttpURLConnection.java:1430)
at java.security.AccessController.doPrivileged(Native Method)
at java.security.AccessController.doPrivileged(AccessController.java:713)
at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1429)
at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:254)
at java.net.URL.openStream(URL.java:1038)
at com.untyped.sbtgraph.Graph$class.downloadAndCache(Graph.scala:155)
at com.untyped.sbtjs.Graph.downloadAndCache(Graph.scala:11)
at com.untyped.sbtgraph.Graph$class.getSource(Graph.scala:41)
at com.untyped.sbtjs.Graph.getSource(Graph.scala:11)
at com.untyped.sbtgraph.Graph$class.getSource(Graph.scala:35)
at com.untyped.sbtjs.Graph.getSource(Graph.scala:11)
at com.untyped.sbtjs.JsmSource$$anonfun$parents$3.apply(JsmSource.scala:11)
at com.untyped.sbtjs.JsmSource$$anonfun$parents$3.apply(JsmSource.scala:10)
at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:244)
at scala.collection.immutable.List.foreach(List.scala:318)
at scala.collection.TraversableLike$class.map(TraversableLike.scala:244)
at scala.collection.AbstractTraversable.map(Traversable.scala:105)
at com.untyped.sbtjs.JsmSource.parents$lzycompute(JsmSource.scala:10)
at com.untyped.sbtjs.JsmSource.parents(JsmSource.scala:8)
at com.untyped.sbtgraph.Graph$class.parents(Graph.scala:172)

Caused by: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target
at sun.security.provider.certpath.SunCertPathBuilder.build(SunCertPathBuilder.java:145)
at sun.security.provider.certpath.SunCertPathBuilder.engineBuild(SunCertPathBuilder.java:131)
at java.security.cert.CertPathBuilder.build(CertPathBuilder.java:280)
at sun.security.validator.PKIXValidator.doBuild(PKIXValidator.java:382)
at sun.security.validator.PKIXValidator.engineValidate(PKIXValidator.java:292)
at sun.security.validator.Validator.validate(Validator.java:260)
at sun.security.ssl.X509TrustManagerImpl.validate(X509TrustManagerImpl.java:324)
at sun.security.ssl.X509TrustManagerImpl.checkTrusted(X509TrustManagerImpl.java:229)

Ok.. I'm trying to run it on java 8.