Emit friendly message when stats aggregation fails running

Summary: Emit a simple info message on terminal whenever aggregation of stats fails for whatever reason, details about the failure will still be available in `toplevel.log`

Reviewed By: jvillard

Differential Revision: D3516339

fbshipit-source-id: fe24d64

infer/lib/python/inferlib/utils.py

@@ -141,7 +141,8 @@ def run_infer_stats_aggregator(infer_out, buck_out=None):
     except subprocess.CalledProcessError as exc:
         output = 'Error while aggregating stats ({ec}): {output}'\
             .format(ec=exc.returncode, output=exc.output)
-        stderr(output)
+        stderr('Info: aggregated performance data are not available in '
+               'this run')
         return output