Pretty-print task config (#1558)

diff --git a/buildkite/bazelci.py b/buildkite/bazelci.py
index f76f53d..d1ede39 100755
--- a/buildkite/bazelci.py
+++ b/buildkite/bazelci.py
@@ -1209,7 +1209,7 @@
             raise BuildkiteException("use_bazel_at_commit cannot be set when use_but is true")
 
         print_collapsed_group(":printer: Printing task config for downstream job...")
-        eprint(json.dumps(task_config))
+        eprint(json.dumps(task_config, indent=2))
 
     tmpdir = tempfile.mkdtemp()
     sc_process = None