fixture 'mocker' not found

I haven’t looked too closely into this bug yet, but the error itself is strange, given that it explicitly lists ‘mocker’ as one of the available fixtures.

I had run tox -r previously and everything passed. Then I upgraded

• pytest (2.9.2) -> 3.0.3
• pytest-mock (1.2) -> 1.4.0

And started seeing this failure.

  @pytest.fixture
  def request(mocker):
E       fixture 'mocker' not found
>       available fixtures: cache, capfd, capsys, doctest_namespace, mock, mocker, monkeypatch, pytestconfig, record_xml_property, recwarn, request, requests_get, tmpdir, tmpdir_factory
>       use 'pytest --fixtures [testpath]' for help on them.

Code looks something like this:

import pytest
from mock import Mock, sentinel
from requests import codes

@pytest.fixture
def request(mocker):
    return Mock((), url='https://test-url.com:8000', cookies=None, headers={})