add a big of debugging info to figure out more abour bot_update failures

Change-Id: If324a6af154c4ded3b4c8d5e07a4740722318a59
BUG:1206377
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/2889824
Auto-Submit: Anthony Polito <apolito@google.com>
Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>

recipes/recipe_modules/bot_update/resources/bot_update.py

@@ -212,7 +212,11 @@ def call(*args, **kwargs):  # pragma: no cover
   hanging_cr = False
   while True:
     for observer in observers:
-      observer.poke()
+      try:
+        observer.poke()
+      except:
+        print('failed to poke, active thread count is %d' % threading.active_count())
+        raise
     buf = proc.stdout.read(BUF_SIZE)
     if not buf:
       break