How do I 'workon' a Python virtualenv in Byobu windows configuration?

Question

I'm trying to configure Byobu that it will start with a few windows ready in my Python virtualenvwrapper project directory. The only thing that needs to be run is the command workon myvirtualenvname.

What I've done now is this.

1. Selected the Screen backend using

   byobu-select-backend
   

2. In ~/.byobu/windows:

   screen -t env2-1 workon env2
   screen -t env2-2 workon env2
   

3. Starting byobu now fails. Running

   byobu
   

   results in a error being shown for a short period of time:

   Cannot exec 'workon': No such file or directory
   

   and Byobu terminates:

   [screen is terminating]
   

I think the issue originates in the way the workon command is defined. As with the virtualenvwrapper documentation, this is being set in ~/.bashrc by sourcing /usr/local/bin/virtualenvwrapper.sh. In the latter file this workon command is defined as a Bash function (function workon {).

How can I make screen/byobu start my windows as defined in the configuration despite it being Bash functions being run in there?

I'm using Ubuntu 12.04 and virtualenv 3.6 (not on 4.x yet as I see it has some backward incompatibilities).