Virtualbox

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* IGuest.create_session() now raises a more descriptive error if
not able to connect with a zero-length password. (sethmlarson PR 70)
* Add sys.executable-derived paths in list to check for vboxapi (sethmlarson PR 69)
* Fix IGuestProcess.execute() on Python 3.x (sethmlarson PR 58)
* Fix errors to not output on Windows platforms. (sethmlarson PR 57)
* Fix error caused by attempting to set any attribute in the COM interface
using setattr raising an error. (Reported by josepegerent, patch by sethmlarson PR 74)

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* Support for 5.0.x VirtualBox.
* Introduce Major.Minor virtualbox build version assertion when creating a VirtualBox
instance.
* Fix to IMachine.export_to (contribution from z00m1n).

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* Cleanup managers at exit (reported by jiml521).
* Add three time check for attribute in xpcom interface object before failing (reported
by shohamp).
* Update library.py to 4.3.28/src/VBox/Main/idl/VirtualBox.xidl

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* This change introduces some significant (potential compatability breaking)
updates from the latest VirtualBox.xidl.
* Bug fixes in IMachine (reported by danikdanik).
* IHost API issue workaround by wndhydrnt.

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* Bug fixes (compatability issue with py26 and virtual keyboard).
* Thanks to contributions by D4rkC4t and Guilherme Moro.

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* Improve error handling and documentation of error types.
* Appliance extension.
* Update to latest API (includes Paravirt provider).
* Thanks to contributions by nilp0inter