added missing cacerts workaround

Author: holgerbrandl

.travis.yml

@@ -26,6 +26,9 @@ install:
   - sudo add-apt-repository -y ppa:openjdk-r/ppa
   - sudo apt-get update
   - sudo apt-get install openjdk-8-jdk
+  # workaround for missing cacerts in openjdk
+  - sudo dpkg --purge --force-depends ca-certificates-java
+  - sudo apt-get install ca-certificates-java
 
 #  - sudo apt-get install -y openjdk-8-jdk
   - sudo apt-get install -y curl unzip zip wget