When the callback causes something that results in changes wrt registered handles, python aborts iteration. Relevant error message: Exception in callback None() handle: <Handle cancelled> Traceback (most recent call last): File "/usr/lib64/python3.5/asyncio/events.py", line 126, in _run self._callback(*self._args) File "/usr/lib64/python3.5/site-packages/libvirtaio.py", line 99, in _handle for callback in self.callbacks.values(): RuntimeError: dictionary changed size during iteration QubesOS/qubes-issues#2805 Signed-off-by: Wojtek Porczyk <woju(a)invisiblethingslab.com&gt; --- libvirtaio.py | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/libvirtaio.py b/libvirtaio.py index d161cd1..46923d8 100644 --- a/libvirtaio.py +++ b/libvirtaio.py @@ -96,7 +96,7 @@ class Descriptor(object): :param int event: The event (from libvirt's constants) being dispatched ''' - for callback in self.callbacks.values(): + for callback in list(self.callbacks.values()): if callback.event is not None and callback.event & event: callback.cb(callback.iden, self.fd, event, callback.opaque) -- 2.9.4