glue-sprite - pkg_resources.DistributionNotFound: PIL==1.1.7

Origin: vendor, https://github.com/jorgebastida/glue/issues/85

Hello. I installed glue-sprite on Ubuntu 13.04 using apt-get but when it was run it gave the following error:

Traceback (most recent call last):
  File "/usr/bin/glue-sprite", line 5, in <module>
    from pkg_resources import load_entry_point
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 2803, in <module>
    working_set.require(__requires__)
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 696, in require
    needed = self.resolve(parse_requirements(requirements))
  File "/usr/lib/python2.7/dist-packages/pkg_resources.py", line 594, in resolve
    raise DistributionNotFound(req)
pkg_resources.DistributionNotFound: PIL==1.1.7

After installing glue using pip, glue-sprite runs without the error.