use importlib in pytest

pipelines/build.sh

@@ -55,7 +55,7 @@ if [ "$JOB_NAME" != "csst_proto" ]; then
   echo "===================== download code style tests ====================="
   curl -O https://csst-tb.bao.ac.cn/code/csst-l1/csst_proto/-/raw/main/pipelines/test_codestyle.py
 fi
-coverage run -m pytest
+coverage run -m pytest --import-mode=importlib
 status_unittest=$?
 
 echo "===================== make coverage ====================="