floh@klappstuhl:~/hg/wfmanage$ /usr/bin/hg pull
abort: requirement 'dotencode' not supported!

You can find much more current mercurial builds at the ubuntu packagers page.
This is how to add them, and get rid of the error.

sudo apt-key adv --keyserver keyserver.ubuntu.com --recv-key 323293EE
sudo add-apt-repository ppa:mercurial-ppa/stable-snapshots
sudo apt-get update
floh@klappstuhl:~/hg/wfmanage$ sudo apt-get upgrade mercurial
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following packages have been kept back:
  linux-headers-server linux-image-server linux-server
The following packages will be upgraded:
  libvirt-bin libvirt0 mercurial mercurial-common
4 upgraded, 0 newly installed, 0 to remove and 3 not upgraded.
Need to get 3,324kB/3,388kB of archives.
After this operation, 2,200kB of additional disk space will be used.
Do you want to continue [Y/n]? y
Get:1 http://ppa.launchpad.net/mercurial-ppa/stable-snapshots/ubuntu/ maverick/main mercurial-common all 2.0.1+2-2f2ca019569f-0ppa1~maverick1 [1,966kB]
Get:2 http://de.archive.ubuntu.com/ubuntu/ maverick-updates/main libvirt-bin amd64 0.8.3-1ubuntu19.4 [791kB]
Get:3 http://de.archive.ubuntu.com/ubuntu/ maverick-updates/main libvirt-bin amd64 0.8.3-1ubuntu19.4 [791kB]
Get:4 http://de.archive.ubuntu.com/ubuntu/ maverick-updates/main libvirt0 amd64 0.8.3-1ubuntu19.4 [567kB]
Fetched 3,031kB in 1min 31s (33.1kB/s)
(Reading database ... 76460 files and directories currently installed.)

....removed 100 lines or more of update triggers here....

Setting up mercurial-common (2.0.1+2-2f2ca019569f-0ppa1~maverick1) ...
Setting up mercurial (2.0.1+2-2f2ca019569f-0ppa1~maverick1) ...
Installing new version of config file /etc/mercurial/hgrc.d/mergetools.rc ...
Installing new version of config file /etc/bash_completion.d/mercurial ...
Processing triggers for libc-bin ...
ldconfig deferred processing now taking place
Processing triggers for python-central ...