Print a warning and continue if no results could be fetched in rebaseline_from_try_jobs.py.

third_party/WebKit/Tools/Scripts/webkitpy/tool/commands/rebaseline_from_try_jobs.py

Index: third_party/WebKit/Tools/Scripts/webkitpy/tool/commands/rebaseline_from_try_jobs.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/tool/commands/rebaseline_from_try_jobs.py b/third_party/WebKit/Tools/Scripts/webkitpy/tool/commands/rebaseline_from_try_jobs.py
index 051ef3fda1ef711a650b17a2cbe2808b8e0349c6..6d8f1118769e18fa330e43957f6a67cc2fb5d4fe 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/tool/commands/rebaseline_from_try_jobs.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/tool/commands/rebaseline_from_try_jobs.py
@@ -46,6 +46,9 @@ class RebaselineFromTryJobs(AbstractParallelRebaselineCommand):
         results_url = self._results_url(try_job.builder_name, try_job.master_name, try_job.build_number)
         builder = self._tool.buildbot.builder_with_name(try_job.builder_name, try_job.master_name)
         layout_test_results = builder.fetch_layout_test_results(results_url)
+        if layout_test_results is None:

[wkorman, 2016/06/29 18:30:17]

Is this preferred to:

if not layout_test_results:

I feel like I see the 'not' more often, but am fine with either.

+            _log.warning('Failed to request layout test results from "%s".', results_url)
+            return []
         return layout_test_results.unexpected_mismatch_results()
 
     def execute(self, options, args, tool):