Virtual Machine with Unity8/Mir Login Crash

Created a virtual machine with VirtualBox with this daily build: http://cdimage.ubuntu.com/daily-live/20160401/

Installed "unity8-desktop-session-mir" through apt. Logged out of VM. Selected Unity8 in greeter and entered password. VM screen blanks, resizes, and shows greeter without password input fields. VM only responds to hitting the "Esc" key, which brings back up the "Retry" button without any password fields. Any attempt to enter a password results in "Authentication Failed". Below is a relevant excerpt from /var/log/lightdm/unity-system-compositor.log:

[2016-04-04 15:31:05.305207] mirplatform: Found graphics driver: mir:mesa-kms (version 0.20.3)
[2016-04-04 15:31:05.305568] mirplatform: Found graphics driver: mir:mesa-x11 (version 0.20.3)
[2016-04-04 15:31:05.307152] mirserver: Starting
[2016-04-04 15:31:05.308860] mircommon: Loading modules from: /usr/lib/x86_64-linux-gnu/mir/server-platform
[2016-04-04 15:31:05.308897] mircommon: Loading module: /usr/lib/x86_64-linux-gnu/mir/server-platform/graphics-mesa-kms.so.8
[2016-04-04 15:31:05.308911] mircommon: Loading module: /usr/lib/x86_64-linux-gnu/mir/server-platform/server-mesa-x11.so.8
[2016-04-04 15:31:05.309350] mircommon: Loading module: /usr/lib/x86_64-linux-gnu/mir/server-platform/input-evdev.so.5
[2016-04-04 15:31:05.310238] mirplatform: Found graphics driver: mir:mesa-kms (version 0.20.3)
[2016-04-04 15:31:05.310255] mirplatform: Found graphics driver: mir:mesa-x11 (version 0.20.3)
[2016-04-04 15:31:05.310344] mirserver: Selected driver: mir:mesa-kms (version 0.20.3)
ERROR: /build/mir-7Eu1Pi/mir-0.20.3+16.04.20160322/src/server/graphics/default_configuration.cpp(132): Throw in function mir::DefaultServerConfiguration::the_graphics_platform()::<lambda()>
Dynamic exception type: boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<std::runtime_error> >
std::exception::what: Exception while creating graphics platform
ERROR: /build/mir-7Eu1Pi/mir-0.20.3+16.04.20160322/src/platforms/mesa/server/common/display_helpers.cpp(256): Throw in function int mir::graphics::mesa::helpers::DRMHelper::open_drm_device(const std::shared_ptr<mir::udev::Context>&)
Dynamic exception type: boost::exception_detail::clone_impl<boost::exception_detail::error_info_injector<std::runtime_error> >
std::exception::what: Error opening DRM device
123, "No medium found"