www/py-django-assets : relax requirement for webassets

[rene]

Summary

Currently www/py-django-assets insists via requirements.txt on having exactly version 0.10 of www/py-webassets installed This makes it impossible to load the pootle binary (see https://reviews.freebsd.org/D1234 ). The proposal is to require at least version 0.10 of webassets.

Test Plan

"import django_assets" from a Python shell still works.

Running the pootle port (WIP):
before:
Traceback (most recent call last):
...
pkg_resources.DistributionNotFound: webassets==0.10

(I had to run ktrace to find the culprit)

after:
Usage: pootle [--config=/path/to/settings.conf] [command] [options]

[wg]