Add in a concurrency aware subunit filter

A live filter for subunit stream that will let us display the
concurrency of the streams as we go.

* This includes the worker id as {#} at the beginning of the lines
* Dumps out stdout/stderr if they are found inline (makes for easier
  debug
* Dumps out pythonlogging on failures if found inline
* Prints skip reasons

Based on I1b529546e005f47aba56b451e1c0d8b0da09fca3, but because
that started as Robert's I couldn't un Abandon it.

Change-Id: Icc99b652e4e8ae85b73bb905a3b704447a63195f
Co-Authored-By: Robert Collins <rbtcollins@hp.com>
diff --git a/tools/pretty_tox_serial.sh b/tools/pretty_tox_serial.sh
index 42ce760..1634b8e 100755
--- a/tools/pretty_tox_serial.sh
+++ b/tools/pretty_tox_serial.sh
@@ -7,7 +7,7 @@
 if [ ! -d .testrepository ]; then
     testr init
 fi
-testr run --subunit $TESTRARGS | subunit2pyunit
+testr run --subunit $TESTRARGS | $(dirname $0)/subunit-trace.py
 retval=$?
 testr slowest
 exit $retval