travis: Replace Trusty with Xenial

.travis.yml

@@ -1,5 +1,5 @@
 sudo: required
-dist: trusty
+dist: xenial
 language: cpp
 
 services:
@@ -35,13 +35,12 @@ before_install:
 install:
   # note that if you are building a slightly different dpdk you will
   # want to avoid the "ln -s /build/dpdk-17.05 deps" step below
-  - sudo apt-get install -y python2.7 python3 python3-pip ruby-dev
+  - sudo apt-get install -y python2.7 python3 python3-pip python3-setuptools ruby-dev
   - sudo gem install ffi fpm
   - pip2 install --user grpcio==1.10 scapy codecov
   - pip3 install --user grpcio==1.10 scapy-python3 coverage
   - "[[ ${COVERAGE:-0} == 0 ]] || sudo apt-get install -y g++-7"  # install gcov-7
   - "[[ ${SANITIZE:-0} == 0 ]] || sudo apt-get install -y llvm-3.8"
-  - "[[ $TAG_SUFFIX != _32 ]] || sudo apt-get install -y lib32gcc1"
   - "docker pull nefelinetworks/bess_build:latest${TAG_SUFFIX} | cat"  # cat suppresses progress bars
 
 before_script:
@@ -89,7 +88,7 @@ deploy:
   skip_cleanup: true
   on:
     tags: true
-    condition: "$VER_CXX = g++-6"
+    condition: "$VER_CXX = g++-7"
 
 notifications:
   slack: nefeli:x5udJ7nDIKjCaCrRYprGc4mw