problems importing from /usr/lib/pyshared/

[Harold]

Dear all,

I recently upgraded my system from ubuntu 11.4 to 12.4 and since run into an issue when trying to import several packages in python2.7, e.g.

harold at ubuntu:~$ python -c 'import gtk'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python2.7/dist-packages/gtk-2.0/gtk/__init__.py", line 30, in <module>
    import gobject as _gobject
  File "/usr/share/pyshared/gobject/__init__.py", line 26, in <module>
    from glib import spawn_async, idle_add, timeout_add, timeout_add_seconds, \
  File "/usr/share/pyshared/glib/__init__.py", line 22, in <module>
    from glib._glib import *
ImportError: No module named _glib

the same, for example, with pysvn:

harold at ubuntu:~$ python -c 'import pysvn'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/share/pyshared/pysvn/__init__.py", line 99, in <module>
    import _pysvn_2_7
ImportError: No module named _pysvn_2_7

After playing around a bit, I realized that I can import said packages without problems, if I delete /usr/lib/pyshared from the python path:

>>> import sys
>>> sys.path
['', '/usr/share/pyshared', '/home/harold', '/usr/lib/python2.7', '/usr/lib/python2.7/plat-linux2', '/usr/lib/python2.7/lib-tk', '/usr/lib/python2.7/lib-old', '/usr/lib/python2.7/lib-dynload', '/usr/local/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages', '/usr/lib/python2.7/dist-packages/PIL', '/usr/lib/python2.7/dist-packages/gst-0.10', '/usr/lib/python2.7/dist-packages/gtk-2.0', '/usr/lib/python2.7/dist-packages/ubuntu-sso-client', '/usr/lib/python2.7/dist-packages/ubuntuone-client', '/usr/lib/python2.7/dist-packages/ubuntuone-control-panel', '/usr/lib/python2.7/dist-packages/ubuntuone-couch', '/usr/lib/python2.7/dist-packages/ubuntuone-installer', '/usr/lib/python2.7/dist-packages/ubuntuone-storage-protocol', '/usr/lib/python2.7/dist-packages/wx-2.8-gtk2-unicode']
>>> del sys.path[1]
>>> import gtk
>>> import pysvn
>>> 

Is /usr/lib/pyshared supposed to be in the python path? If not, how can I ensure that it is not included? Where is PYTHONPATH initialized by default, anyway?

Thanks, harold.