simplify CI horovod (#4951)

* simplify CI horovod

* reorder

Author: Borda

tests/__init__.py

@@ -6,8 +6,10 @@
 PROJECT_ROOT = os.path.dirname(TEST_ROOT)
 TEMP_PATH = os.path.join(PROJECT_ROOT, 'test_temp')
 
+# todo: this setting `PYTHONPATH` may not be used by other evns like Conda for import packages
 if PROJECT_ROOT not in os.getenv('PYTHONPATH', ""):
-    os.environ['PYTHONPATH'] = f'{PROJECT_ROOT}:{os.environ.get("PYTHONPATH", "")}'
+    splitter = ":" if os.environ.get("PYTHONPATH", "") else ""
+    os.environ['PYTHONPATH'] = f'{PROJECT_ROOT}{splitter}{os.environ.get("PYTHONPATH", "")}'
 
 # generate a list of random seeds for each test
 RANDOM_PORTS = list(np.random.randint(12000, 19000, 1000))

tests/models/data/horovod/train_default_model.py

@@ -21,9 +21,8 @@
 import os
 import sys
 
-PATH_HERE = os.path.abspath(os.path.dirname(__file__))
-PATH_ROOT = os.path.abspath(os.path.join(PATH_HERE, '..', '..', '..', '..'))
-sys.path.insert(0, os.path.abspath(PATH_ROOT))
+# this is need as e.g. Conda do not uses `PYTHONPATH` env var as pip or/and virtualenv
+sys.path = os.getenv('PYTHONPATH').split(':') + sys.path
 
 from pytorch_lightning import Trainer  # noqa: E402
 from pytorch_lightning.callbacks import ModelCheckpoint  # noqa: E402
@@ -34,11 +33,6 @@
 else:
     print('You requested to import Horovod which is missing or not supported for your OS.')
 
-
-# Move project root to the front of the search path, as some imports may have reordered things
-idx = sys.path.index(PATH_ROOT)
-sys.path[0], sys.path[idx] = sys.path[idx], sys.path[0]
-
 from tests.base import EvalModelTemplate  # noqa: E402
 from tests.base.develop_pipelines import run_prediction  # noqa: E402
 from tests.base.develop_utils import set_random_master_port, reset_seed  # noqa: E402