cubicweb-file #3825324 pip install : missing dependency to PIL [open]

in virtualenv/pip setup I get the following traceback on a instance creation

File "/home/arthur/.virtualenvs/cubicweb/share/cubicweb/cubes/file/entities.py", line 123, in <module>
  from PIL.Image import open as pilopen
ImportError: No module named PIL.Image
prioritynormal
typebug
done in<not specified>
closed by<not specified>