Fails to start when just issued executable's name ('updf'); need to issue full path ('/usr/bin/updf').

When I want to start updf by just typing 'updf' in a terminal, I get the following error:

== %< ==

Traceback (most recent call last):
  File "/sbin/updf", line 37, in <module>
    from updf import main
ImportError: No module named updf

== >% ==

However, explicitely typing '/usr/bin/updf' works.

For executables in /usr/bin I expect that I can run them by just typing the name of the executable, that what PATH environment variable is for.

Tested with updf version 0.0.2.4, up-to-date-bazaar-checkout on 2016-09-24, on Arch Linux, AUR pckage build (https://aur.archlinux.org/packages/updf-bzr).