1 files changed, 8 insertions, 2 deletions
diff --git a/synapse/util/logcontext.py b/synapse/util/logcontext.py
index d660ec785b..bbadeec922 100644
--- a/synapse/util/logcontext.py
+++ b/synapse/util/logcontext.py
@@ -92,6 +92,7 @@ class LoggingContext(object):
 
         def __nonzero__(self):
             return False
+        __bool__ = __nonzero__  # python3
 
     sentinel = Sentinel()
 
@@ -304,7 +305,12 @@ def run_in_background(f, *args, **kwargs):
     deferred returned by the funtion completes.
 
     Useful for wrapping functions that return a deferred which you don't yield
-    on.
+    on (for instance because you want to pass it to deferred.gatherResults()).
+
+    Note that if you completely discard the result, you should make sure that
+    `f` doesn't raise any deferred exceptions, otherwise a scary-looking
+    CRITICAL error about an unhandled error will be logged without much
+    indication about where it came from.
     """
     current = LoggingContext.current_context()
     res = f(*args, **kwargs)
@@ -340,7 +346,7 @@ def make_deferred_yieldable(deferred):
     returning a deferred. Then, when the deferred completes, restores the
     current logcontext before running callbacks/errbacks.
 
-    (This is more-or-less the opposite operation to preserve_fn.)
+    (This is more-or-less the opposite operation to run_in_background.)
     """
     if isinstance(deferred, defer.Deferred) and not deferred.called:
         prev_context = LoggingContext.set_current_context(LoggingContext.sentinel)