Copy the certifcats in the insatlled Java VM https://stackoverflow.com/questions/50712164/clojure-build-failed-on-travis-ci-with-openjdk-9-during-lein-deps/50745344#50745344

Author: Volker

.travis.yml

@@ -10,4 +10,14 @@ jdk:
   - openjdk10
   - openjdk11
   - openjdk-ea
+
+matrix:
+  include:
+    - jdk: openjdk11
+      before_install: &fix_certs
+        - rm "${JAVA_HOME}/lib/security/cacerts"
+        - ln -s /etc/ssl/certs/java/cacerts "${JAVA_HOME}/lib/security/cacerts"
+    - jdk: openjdk-ea
+      before_install: *fix_certs
+
 script: ./gradlew check benchmark