Update PIL import

Review Request #7876 — Created Jan. 15, 2016 and submitted — Latest diff uploaded

Information

Djblets
release-0.8.x

Reviewers

Previously, if PIL's Image library could not be imported, the Image
module would be imported. However, this is not a good way to import PIL
becuase it masks the errors from the first import, which can occur if
some dependencies (such as libtiff or libjpeg) are missing.

  • Ran unit tests.