Enable output for test failures.

.travis.yml

@@ -17,7 +17,7 @@ env:
 script:
   - cmake -DCMAKE_BUILD_TYPE=$BUILD_TYPE -DFMT_EXTRA_TESTS=ON .
   - make -j4
-  - make test
+  - CTEST_OUTPUT_ON_FAILURE=1 make test
 
 after_failure:
   - cat Testing/Temporary/LastTest.log

appveyor.yml

@@ -1,4 +1,5 @@
 environment:
+  - CTEST_OUTPUT_ON_FAILURE: 1
   matrix:
   - Build: msvc
     Config: Debug