Test failure preparing interfaces-openvswitch

I have seen during the last days some failures for the test main/interfaces-openvswitch

The issue is a timeout trying to install openvswitch-switch

+ apt install -y --no-install-recommends openvswitch-switch
WARNING: apt does not have a stable CLI interface. Use with caution in scripts.
Reading package lists...
Setting up python-six (1.10.0-3) ...
Setting up openvswitch-common (2.5.2-0ubuntu0.16.04.1) ...
Setting up openvswitch-switch (2.5.2-0ubuntu0.16.04.1) ...
update-alternatives: using /usr/lib/openvswitch-switch/ovs-vswitchd to provide /usr/sbin/ovs-vswitchd (ovs-vswitchd) in auto mode

<kill-timeout reached>

I reexecuted more than 300 times in different configurations and combining with other testst and I could not reproduce the error, anyone has a clue about what could be causing this?

Here some links to the error:
. https://travis-ci.org/snapcore/snapd/builds/235819260
. https://travis-ci.org/snapcore/snapd/builds/235813091
. https://travis-ci.org/snapcore/snapd/builds/236373041