Merge pull request #388 from ferdnyc/travis-fail-ffmpeg4

Travis: allow FFmpeg4 build failures

Author: ferdnyc

.travis.yml

@@ -32,6 +32,11 @@ addons:
     - libswresample-dev
 
 matrix:
+
+  # The FFmpeg4 PPA is currently down as a protest
+  allow_failures:
+  - env: BUILD_VERSION=ffmpeg4
+
   include:
     - name: "FFmpeg 2 GCC (Ubuntu 16.04 Xenial)"
       env: BUILD_VERSION=ffmpeg2