CI should fail when code isn't formatted.

.appveyor.yml

@@ -365,6 +365,7 @@ build_script:
 
 test_script:
   - python tools\lint.py
+  - python tools\test_format.py
   - ps: Exec { & python tools\test.py $env:DENO_BUILD_PATH }
 
 after_test:

.travis.yml

@@ -87,6 +87,7 @@ before_script:
 - ./tools/setup.py
 script:
 - ./tools/lint.py
+- ./tools/test_format.py
 - bash -c "sleep 2100; pkill ninja" &
 - ./tools/build.py -j2
 - ./tools/test.py $DENO_BUILD_PATH

tools/test_format.py

+#!/usr/bin/env python
+# This program fails if ./tools/format.py changes any files.
+
+import sys
+import util
+import sys
+import subprocess
+
+
+def main(argv):
+    util.run([sys.executable, "tools/format.py"])
+    output = util.run_output(
+        ["git", "status", "-uno", "--porcelain", "--ignore-submodules"])
+    if len(output) > 0:
+        print "Run tools/format.py "
+        print output
+        sys.exit(1)
+
+
+if __name__ == '__main__':
+    main(sys.argv)