python: don't mask libvirt errors
python: don't mask libvirt errors

A user reported this crash when using python bindings:

  File "/home/nox/workspace/NOX/src/NOX/hooks.py", line 134, in trigger
    hook.trigger(event)
  File "/home/nox/workspace/NOX/src/NOX/hooks.py", line 33, in trigger
    self.handlers[event]()
  File "/home/nox/workspace/NOX/hooks/volatility.py", line 81, in memory_dump
    for block in Memory(self.ctx):
  File "/home/see/workspace/NOX/src/NOX/lib/libtools.py", line 179, in next
    libvirt.VIR_MEMORY_PHYSICAL)
  File "/usr/lib/python2.7/dist-packages/libvirt.py", line 1759, in memoryPeek
    ret = libvirtmod.virDomainMemoryPeek(self._o, start, size, flags)
SystemError: error return without exception set

In the python bindings, returning NULL makes python think an
exception was thrown, while returning the None object lets the
wrappers know that a libvirt error exists.

Reported by Nox DaFox, fix suggested by Dan Berrange.

* python/libvirt-override.c (libvirt_virDomainBlockPeek)
(libvirt_virDomainMemoryPeek): Return python's None object, so
wrapper knows to check libvirt error.

olafhering/libvirt,jfehlig/libvirt,novel/fbsd-libvirt,zippy2/libvirt,siboulet/libvirt-openvz,emaste/libvirt,rlaager/libvirt,VenkatDatta/libvirt,olafhering/libvirt,novel/fbsd-libvirt,datto/libvirt,warewolf/libvirt,libvirt/libvirt,elmarco/libvirt,crobinso/libvirt,andreabolognani/libvirt,datto/libvirt,warewolf/libvirt,trainstack/libvirt,nertpinx/libvirt,elmarco/libvirt,trainstack/libvirt,iam-TJ/libvirt,elmarco/libvirt,andreabolognani/libvirt,jardasgit/libvirt,nertpinx/libvirt,agx/libvirt,warewolf/libvirt,crobinso/libvirt,jeckersb/libvirt,jeckersb/libvirt,libvirt/libvirt,fabianfreyer/libvirt,novel/fbsd-libvirt,jfehlig/libvirt,iam-TJ/libvirt,taget/libvirt,datto/libvirt,zhlcindy/libvirt-1.1.4-maintain,crobinso/libvirt,trainstack/libvirt,nertpinx/libvirt,taget/libvirt,jeckersb/libvirt,siboulet/libvirt-openvz,libvirt/libvirt,zhlcindy/libvirt-1.1.4-maintain,eskultety/libvirt,jfehlig/libvirt,elmarco/libvirt,jeckersb/libvirt,shugaoye/libvirt,rlaager/libvirt,shugaoye/libvirt,trainstack/libvirt,nertpinx/libvirt,cbosdo/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,iam-TJ/libvirt,zhlcindy/libvirt-1.1.4-maintain,emaste/libvirt,warewolf/libvirt,andreabolognani/libvirt,cbosdo/libvirt,iam-TJ/libvirt,jardasgit/libvirt,agx/libvirt,novel/fbsd-libvirt,emaste/libvirt,novel/fbsd-libvirt,warewolf/libvirt,VenkatDatta/libvirt,eskultety/libvirt,eskultety/libvirt,shugaoye/libvirt,jardasgit/libvirt,datto/libvirt,zippy2/libvirt,iam-TJ/libvirt,crobinso/libvirt,eskultety/libvirt,agx/libvirt,jeckersb/libvirt,novel/fbsd-libvirt,rlaager/libvirt,emaste/libvirt,fabianfreyer/libvirt,olafhering/libvirt,zippy2/libvirt,emaste/libvirt,trainstack/libvirt,elmarco/libvirt,nertpinx/libvirt,warewolf/libvirt,andreabolognani/libvirt,novel/fbsd-libvirt,siboulet/libvirt-openvz,cbosdo/libvirt,bjzhang/libvirt,bjzhang/libvirt,cbosdo/libvirt,fabianfreyer/libvirt,taget/libvirt,jardasgit/libvirt,jardasgit/libvirt,emaste/libvirt,novel/fbsd-libvirt,bjzhang/libvirt,trainstack/libvirt,zhlcindy/libvirt-1.1.4-maintain,zippy2/libvirt,olafhering/libvirt,VenkatDatta/libvirt,cbosdo/libvirt,bjzhang/libvirt,jeckersb/libvirt,shugaoye/libvirt,shugaoye/libvirt,eskultety/libvirt,jeckersb/libvirt,rlaager/libvirt,warewolf/libvirt,jfehlig/libvirt,iam-TJ/libvirt,VenkatDatta/libvirt,novel/fbsd-libvirt,zhlcindy/libvirt-1.1.4-maintain,agx/libvirt,bjzhang/libvirt,emaste/libvirt,fabianfreyer/libvirt,siboulet/libvirt-openvz,taget/libvirt,taget/libvirt,andreabolognani/libvirt,iam-TJ/libvirt,agx/libvirt,datto/libvirt,trainstack/libvirt,rlaager/libvirt,libvirt/libvirt,siboulet/libvirt-openvz