lint: fix quoting style everywhere

BUG=chromium:990019
TEST=`cros lint` is clean & CQ passes

Change-Id: I012966d34a45a01b3a940414b24316aee4ffe8af
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1731476
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
Reviewed-by: Will Bradley <wbbradley@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/sysmon/puppet_metrics_unittest.py b/scripts/sysmon/puppet_metrics_unittest.py
index 648f3c7..2495527 100644
--- a/scripts/sysmon/puppet_metrics_unittest.py
+++ b/scripts/sysmon/puppet_metrics_unittest.py
@@ -19,7 +19,7 @@
 from chromite.scripts.sysmon import puppet_metrics
 
 
-_SUMMARY = '''\
+_SUMMARY = """\
 ---
   version:
     config: 1499979608
@@ -56,7 +56,7 @@
     failure: 0
     success: 7
     total: 7%
-'''
+"""
 
 
 class TestPuppetRunSummary(cros_test_lib.TestCase):