IRCv3 allows you to put names in like #channel1,#channel2 which works in

Pidgin 2 and other clients, but the

Purple.ProtocolConversations.join_channel_async function really only works for

a single channel and the channel join dialog was meant for a single channel.
So this solution isn't ideal, but it's better than creating a conversation

named #channel1,#channel2 at least for the time being.

Attempted to join #channel1,#channel2 and instead got the error message.