[tor-dev] txtorcon 'all_routers' issue

[meejah]

As per https://github.com/meejah/txtorcon/issues/203 all released
versions of txtorcon that have TorState.all_routers will, upon a
NEWCONSENSUS event, make this set empty.  There is already a fix on
master for the real issue and it will be in the next release.

For users of released versions there is a workaround, pointed out by
evilaliv3: simply use TorState.routers.values() instead.

Cheers,
meejah