papered over bug in virtapt

[torbenh3]

after 478b26e ("pkgutils: dont fallback to nonvirtapt code, when virtapt is avail") was applied.
a bug in virtapt was uncovered. Which was handled by dumb fallback Code.
To fix this problem the commit was reverted:
41f7e09 ("Revert "pkgutils: dont fallback to nonvirtapt code, when virtapt is avail"")

` multiprocessing.managers.RemoteError:
---------------------------------------------------------------------------
Traceback (most recent call last):
File "/usr/lib/python2.7/multiprocessing/managers.py", line 207, in handle_request
result = func(c, *args, **kwds)
File "/usr/lib/python2.7/multiprocessing/managers.py", line 386, in create
obj = callable(*args, **kwds)
File "/home/jogness/tmpfs/elbe/elbepack/virtapt.py", line 97, in init
self.cache = apt_pkg.Cache()
Error: W:Updating from such a repository can't be done securely, and is therefore disabled by default., W:See apt-secure(8) manpage for repository creation and user configuration details., E:The value 'jessie' is invalid for APT::Default-Release as such a release is not available in the sources
---------------------------------------------------------------------------

`

[manut]

duplicate of #139