diff --git a/.github/workflows/run-unit-tests_conda-forge.yml b/.github/workflows/run-unit-tests_conda-forge.yml
index 7a0ef70..2fc82a4 100644
--- a/.github/workflows/run-unit-tests_conda-forge.yml
+++ b/.github/workflows/run-unit-tests_conda-forge.yml
@@ -33,6 +33,9 @@ jobs:
         conda-solver: libmamba
 
     - name: Install dependencies
+      # Note that conda-forge OpenCV 4.9 package has *GL dependencies that are not satisfied by
+      # GitHub's Ubuntu image, so 'opencv-python-headless' is installed with pip below.
+      # TODO: change this if a headless conda-forge version becomes available
       run: |
         conda info
         conda install -c conda-forge rasterio click tqdm pyyaml fsspec requests aiohttp pytest pytest-cov
diff --git a/orthority/__init__.py b/orthority/__init__.py
index 99c57c0..aa672fa 100644
--- a/orthority/__init__.py
+++ b/orthority/__init__.py
@@ -14,18 +14,20 @@
 # If not, see <https://www.gnu.org/licenses/>.
 
 """Orthorectification toolkit."""
-import logging
 import os
-import pathlib
 
 # enable on-demand download and caching of proj transformation grids (NB must be done before
 # importing rasterio)
 os.environ.update(PROJ_NETWORK='ON')
 
+import logging
+import pathlib
+
 from orthority.enums import Compress, Interp
 from orthority.factory import FrameCameras, RpcCameras
 from orthority.ortho import Ortho
 
+
 # Add a NullHandler to the package logger to hide logs by default.  Applications can then add
 # their own handler(s).
 log = logging.getLogger(__name__)
diff --git a/orthority/cli.py b/orthority/cli.py
index b319ff5..7458ac5 100644
--- a/orthority/cli.py
+++ b/orthority/cli.py
@@ -1193,6 +1193,4 @@ def simple_ortho(argv=None):
 if __name__ == '__main__':
     cli()
 
-# TODO: test CLI exceptions are meaningful
-
 ##
diff --git a/tests/__init__.py b/tests/__init__.py
index e69de29..d87fb2d 100644
--- a/tests/__init__.py
+++ b/tests/__init__.py
@@ -0,0 +1,20 @@
+# Copyright The Orthority Contributors.
+#
+# This file is part of Orthority.
+#
+# Orthority is free software: you can redistribute it and/or modify it under the terms of the GNU
+# Affero General Public License as published by the Free Software Foundation, either version 3 of
+# the License, or (at your option) any later version.
+#
+# Orthority is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without
+# even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License along with Orthority.
+# If not, see <https://www.gnu.org/licenses/>.
+
+# enable on-demand download and caching of proj transformation grids (NB must be done before
+# importing rasterio)
+import os
+
+os.environ.update(PROJ_NETWORK='ON')
diff --git a/tests/test_camera.py b/tests/test_camera.py
index d9d7190..4ba254c 100644
--- a/tests/test_camera.py
+++ b/tests/test_camera.py
@@ -15,28 +15,23 @@
 
 from __future__ import annotations
 
+from pathlib import Path
+from typing import Sequence
+
+import cv2
 import numpy as np
 import pytest
-from pathlib import Path
 import rasterio as rio
-import cv2
 from rasterio.transform import from_bounds
-from typing import Sequence
 
+from orthority import utils
 from orthority.camera import (
-    BrownCamera,
-    Camera,
-    create_camera,
-    FisheyeCamera,
-    FrameCamera,
-    OpenCVCamera,
-    PinholeCamera,
+    BrownCamera, Camera, create_camera, FisheyeCamera, FrameCamera, OpenCVCamera, PinholeCamera,
     RpcCamera,
 )
 from orthority.enums import CameraType, Interp
 from orthority.errors import CameraInitError, OrthorityWarning
-from tests.conftest import _dem_offset, _dem_gain, checkerboard, ortho_bounds, create_zsurf
-from orthority import utils
+from tests.conftest import _dem_offset, checkerboard, create_zsurf, ortho_bounds
 
 
 @pytest.mark.parametrize(
@@ -129,13 +124,14 @@ def test_frame_update(im_size: tuple, focal_len: float, sensor_size: tuple, xyz:
     assert np.all(camera._R != 0)
 
 
-@pytest.mark.parametrize('cam_type',
-    [CameraType.pinhole, CameraType.opencv, CameraType.brown, CameraType.fisheye]
+@pytest.mark.parametrize(
+    'cam_type', [CameraType.pinhole, CameraType.opencv, CameraType.brown, CameraType.fisheye]
 )
 def test_frame_update_error(
     cam_type: CameraType, im_size: tuple, focal_len: float, sensor_size: tuple
 ):
-    """Test an error is raised if a ``FrameCamera`` is used before initialising exterior parameters.
+    """Test an error is raised if a ``FrameCamera`` is used before initialising exterior
+    parameters.
     """
     camera = create_camera(cam_type, im_size, focal_len, sensor_size=sensor_size)
 
@@ -874,9 +870,7 @@ def test_frame_world_boundary_equiv(camera: str, camera_und: str, request: pytes
     assert xyz == pytest.approx(xyz_und, abs=1e-6)
 
 
-@pytest.mark.parametrize(
-    'camera', ['pinhole_camera', 'rpc_camera']
-)
+@pytest.mark.parametrize('camera', ['pinhole_camera', 'rpc_camera'])
 def test_world_boundary_errors(camera: str, request: pytest.FixtureRequest):
     """Test ``Camera.world_boundary()`` error conditions."""
     camera: Camera = request.getfixturevalue(camera)