Trying a different config. Now we try executing a gem install in the before_install part of our python based language block.

.travis.yml

@@ -1,15 +1,8 @@
-matrix:
-  include:
-    - language: ruby
-      rvm:
-        - 2.2
-        - jruby
-        - 2.0.0-p247
-      install: gem install zsteg
-
-    - language: python
+language: python
 python:
   - 3.6
+before_install:
+  - gem install zsteg
 install:
   - pip install -r requirements.txt
 script: