Build error at django-constance git checkout

[schneimi]

Two days before building worked just fine, today I run into following error:

Collecting django-constance[database] from git+git://github.com/haiwen/django-constance.git@751f7f8b60651a2828e4a535a47fc05b907883da#egg=django-constance[database] (from -r requirements.txt (line 11))
  Cloning git://github.com/haiwen/django-constance.git (to 751f7f8b60651a2828e4a535a47fc05b907883da) to /tmp/pip-build-2PSWzO/django-constance
  Could not find a tag or branch '751f7f8b60651a2828e4a535a47fc05b907883da', assuming commit.
fatal: reference is not a tree: 751f7f8b60651a2828e4a535a47fc05b907883da
Command "git checkout -q 751f7f8b60651a2828e4a535a47fc05b907883da" failed with error code 128 in /tmp/pip-build-2PSWzO/django-constance