Set the import mode for dask tests (rapidsai#2142)

This PR fixes the underlying issue that led us to pin pytest in rapidsai#2137. For now, this PR leaves pytest pinned since there are other issues with pytest 8 and plugin interactions that have broken other RAPIDS libraries so I figured this was safer and we could relax the pin when the rest of RAPIDS does. However, if preferred I'm happy to undo the pinning in this PR too.

Authors:
  - Vyas Ramasubramani (https://github.com/vyasr)

Approvers:
  - Corey J. Nolet (https://github.com/cjnolet)
  - Ray Douglass (https://github.com/raydouglass)

URL: rapidsai#2142

ci/run_raft_dask_pytests.sh

@@ -6,4 +6,4 @@ set -euo pipefail
 # Support invoking run_raft_dask_pytests.sh outside the script directory
 cd "$(dirname "$(realpath "${BASH_SOURCE[0]}")")"/../python/raft-dask/raft_dask
 
-pytest --cache-clear "$@" test
+pytest --cache-clear --import-mode=append "$@" test

ci/test_wheel_raft_dask.sh

@@ -14,10 +14,10 @@ python -m pip install "raft-dask-${RAPIDS_PY_CUDA_SUFFIX}[test]>=0.0.0a0" --find
 test_dir="python/raft-dask/raft_dask/test"
 
 # rapids-logger "pytest raft-dask"
-# python -m pytest ${test_dir}
+# python -m pytest --import-mode=append ${test_dir}
 
 # rapids-logger "pytest raft-dask (ucx-py only)"
-# python -m pytest ${test_dir} --run_ucx
+# python -m pytest --import-mode=append ${test_dir} --run_ucx
 
 rapids-logger "pytest raft-dask (ucxx only)"
-python -m pytest ${test_dir} --run_ucxx
+python -m pytest --import-mode=append ${test_dir} --run_ucxx