Fix format string.

After changing this to '%f%' instead of just '%' this doesn't
work anymore. It should be '%f%%' instead.

BUG=
TBR=iannucci@chromium.org

Review URL: https://codereview.chromium.org/1156023008

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@295539 0039d316-1c4b-4281-b951-d872f2087c98

testing_support/coverage_utils.py

@@ -64,7 +64,7 @@ def covered_main(includes, require_native=None, required_percentage=100.0):
 
   COVERAGE.stop()
   if COVERAGE.report() < required_percentage:
-    print 'FATAL: not at required %f% coverage.' % required_percentage
+    print 'FATAL: not at required %f%% coverage.' % required_percentage
     retcode = 2
 
   return retcode