Code review comment for lp:~robert-ancell/mir/vt-option

Cool, works nicely now.

I noticed a little bug, but that's only a side-effect and not really part of this proposal. Running as non-root gives a slightly inaccurate error message now:

(run from tty3) mir_demo_server_shell --vt 6
ERROR: /home/dan/bzr/mir/tmp.vt/src/server/graphics/gbm/linux_virtual_terminal.cpp(197): Throw in function int mir::graphics::gbm::LinuxVirtualTerminal::open_vt(int)
Dynamic exception type: boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<std::runtime_error> >
std::exception::what: Failed to open current VT <---- This is wrong. It's not trying to open the "current" one.
[boost::errinfo_errno_*] = 13, "Permission denied"
[boost::errinfo_file_name_*] = /dev/tty6