An attempt to make Travis linux builds work

Following:
https://docs.travis-ci.com/user/common-build-problems/?utm_source=blog&utm_medium=web&utm_campaign=ftp_blog#ftpsmtpother-protocol-do-not-work

.travis.yml

@@ -18,13 +18,15 @@ addons:
   apt:
     packages:
     - telnet
+    - openvpn
     update: true
   homebrew:
     packages:
     - telnet
     update: true
 
 before_install:
+  - if [ $TRAVIS_OS_NAME = linux ]; then sudo openvpn path/to/conf.ovpn &>>openvpn-client.log &; fi
   - if [ $TRAVIS_OS_NAME = windows ]; then choco install telnet -y; fi
 
 ## uncomment the following lines to allow failures on nightly julia