root@seta00:~# apt-get install mercurial
Reading package lists... Done
Building dependency tree
Reading state information... Done
Suggested packages:
  qct wish vim emacs kdiff3 tkdiff meld xxdiff
The following NEW packages will be installed:
  mercurial
0 upgraded, 1 newly installed, 0 to remove and 28 not upgraded.
Need to get 0B/55.5kB of archives.
After this operation, 283kB of additional disk space will be used.
Selecting previously deselected package mercurial.
(Reading database ... 53813 files and directories currently installed.)
Unpacking mercurial (from .../mercurial_1.6.3-1_amd64.deb) ...
Setting up mercurial (1.6.3-1) ...

Creating config file /etc/mercurial/hgrc.d/hgext.rc with new version
Processing triggers for python-support ...
root@seta00:~# hg
Traceback (most recent call last):
  File "/usr/local/bin/hg", line 4, in <module>
    import pkg_resources
  File "/usr/lib/python2.6/dist-packages/pkg_resources.py", line 2675, in <module>
    parse_requirements(__requires__), Environment()
  File "/usr/lib/python2.6/dist-packages/pkg_resources.py", line 552, in resolve
    raise DistributionNotFound(req)
pkg_resources.DistributionNotFound: mercurial==1.7.2