10293: Don't try to json decode empty output file to reduce spurious errors.

diff --git a/sdk/cwl/arvados_cwl/runner.py b/sdk/cwl/arvados_cwl/runner.py
index 6b5cd71b167a1346e18f1bbecdb1a9e55651e326..178285d1b323a377e73206e46c262c3da97cbd03 100644 (file)
--- a/sdk/cwl/arvados_cwl/runner.py
+++ b/sdk/cwl/arvados_cwl/runner.py
@@ -204,7 +204,8 @@ class Runner(object):
                                                            keep_client=self.arvrunner.keep_client,
                                                            num_retries=self.arvrunner.num_retries)
                 with outc.open("cwl.output.json") as f:
-                    outputs = json.load(f)
+                    if f.size() > 0:
+                        outputs = json.load(f)
                 def keepify(fileobj):
                     path = fileobj["location"]
                     if not path.startswith("keep:"):