fix cargo fmt

mbrysa · mbrysa · commit f5b351ce0f52 · 2020-02-08T17:13:38.000+01:00
taken from SpinResearch#74
diff --git a/.travis.yml b/.travis.yml
@@ -24,7 +24,7 @@ matrix:
       before_script:
         - rustup component add rustfmt-preview
       script:
-        - cargo fmt --all -- --write-mode=diff
+        - cargo fmt --all -- --check
     - env: NAME='kcov'
       sudo: required # travis-ci/travis-ci#9061
       before_script:
