Undefined name: errors

[cclauss]

Where is errors defined?
% flake8 . --count --select=E9,F63,F7,F82 --show-source --statistics

./pinject/pinject/__init__.py:32:23: F821 undefined name 'errors'
for thing_name in dir(errors):
                      ^
./pinject/pinject/__init__.py:33:21: F821 undefined name 'errors'
    thing = getattr(errors, thing_name)
                    ^
2     F821 undefined name 'errors'
2