try to install and run luatex on travis

.travis.yml

@@ -8,9 +8,12 @@ install:
 script:
   - tox -e lint,py35
 sudo: false
-# addons:
-#   apt:
-#     packages:
+addons:
+  apt:
+    sources:
+      - sourceline: 'ppa:texlive-backports/ppa'
+    packages:
+      - luatex
 #     - texlive-latex-base
 #     - latex-xcolor
 #     - texlive-latex-extra

test/test_book/test_compilation.py

@@ -122,8 +122,8 @@ class FileTest(unittest.TestCase, metaclass=dynamic.DynamicTest):
     @classmethod
     def _create_compilation_test(cls, base, onthefly=False):
         """Return a function testing that `base.tex` is correctly compiled."""
-        @unittest.skipIf('CI' in os.environ,
-                         "Travis or AppVeyor does not support lualatex compilation yet")
+        @unittest.skipIf('APPVEYOR' in os.environ,
+                         "AppVeyor does not support lualatex compilation yet")
         def test_compilation(self):
             """Test that `base` is rendered to pdf."""
             # Check compilation