[CodeStyle] add CI script to prevent future import (#46466)

tools/check_file_diff_approvals.sh

@@ -284,6 +284,12 @@ if [ "${INVALID_UNITTEST_ASSERT_CHECK}" != "" ] && [ "${GIT_PR_ID}" != "" ]; the
     check_approval 1 16605440 6836917
 fi
 
+UNNECESSARY_FUTURE_IMPORT=`echo "$ALL_ADDED_LINES" | grep -E '\+\s*from __future__ import .+(nested_scopes|generators|division|absolute_import|with_statement|print_function|unicode_literals|generator_stop)' || true`
+if [ "${UNNECESSARY_FUTURE_IMPORT}" != "" ] && [ "${GIT_PR_ID}" != "" ]; then
+    echo_line="This feature is already mandatory in the Python3.7+, no need to import it from __future__.\nPlease modify the code below. If anything is unclear, please read the Python __future__ module docs [ https://docs.python.org/3/library/__future__.html ]. If it is a mismatch, please request luotao1 (Recommend) or jzhang533 review and approve.\nThe code that do not meet the specification are as follows:\n${UNNECESSARY_FUTURE_IMPORT}\n"
+    check_approval 1 luotao1 jzhang533
+fi
+
 HAS_MODIFIED_PHI_FILES=`git diff --name-only upstream/$BRANCH | grep "paddle/phi/" || true`
 PHI_INCLUDE_FLUID_FILES=""
 for CHANGE_FILE in ${HAS_MODIFIED_PHI_FILES}; do