Revert "Run CI unittests in parallel (#3445)" (#3480)

This reverts commit 4fcaee0f.

.circleci/unittest/linux/scripts/environment.yml

@@ -5,8 +5,6 @@ channels:
   - conda-forge
 dependencies:
   - pytest
-  - pytest-xdist
-  - pytest-timeout
   - pytest-cov
   - codecov
   - pip

.circleci/unittest/linux/scripts/run_test.sh

@@ -6,20 +6,5 @@ eval "$(./conda/bin/conda shell.bash hook)"
 conda activate ./env
 
 export PYTORCH_TEST_WITH_SLOW='1'
-if [ "${CU_VERSION:-}" == cpu ] ; then
-    NUMPROCESSES="auto"
-    export OMP_NUM_THREADS="1"
-else
-    NUMPROCESSES="1"
-fi
-
 python -m torch.utils.collect_env
-pytest \
-    --numprocesses=$NUMPROCESSES \
-    --timeout=300 \
-    --cov=torchvision \
-    --junitxml=test-results/junit.xml \
-    --verbose \
-    --durations 20 \
-    --ignore=test/test_datasets_download.py \
-    test
+pytest --cov=torchvision --junitxml=test-results/junit.xml -v --durations 20 test --ignore=test/test_datasets_download.py

.circleci/unittest/windows/scripts/environment.yml

@@ -5,8 +5,6 @@ channels:
   - conda-forge
 dependencies:
   - pytest
-  - pytest-xdist
-  - pytest-timeout
   - pytest-cov
   - codecov
   - pip

.circleci/unittest/windows/scripts/run_test.sh

@@ -6,20 +6,5 @@ eval "$(./conda/Scripts/conda.exe 'shell.bash' 'hook')"
 conda activate ./env
 
 export PYTORCH_TEST_WITH_SLOW='1'
-if [ "${CU_VERSION:-}" == cpu ] ; then
-    NUMPROCESSES="auto"
-    export OMP_NUM_THREADS="1"
-else
-    NUMPROCESSES="1"
-fi
-
 python -m torch.utils.collect_env
-pytest \
-    --numprocesses=$NUMPROCESSES \
-    --timeout=300 \
-    --cov=torchvision \
-    --junitxml=test-results/junit.xml \
-    --verbose \
-    --durations 20 \
-    --ignore=test/test_datasets_download.py \
-    test
+pytest --cov=torchvision --junitxml=test-results/junit.xml -v --durations 20 test --ignore=test/test_datasets_download.py