tests: use environment variable indirectly Using environment variable directly in heredoc python code will cause syntax error at checking module importation by import-checker.py strictly, because "$varname" is invalid in Python syntax. "$varname" becomes valid after environment variable substitution by shell at writing text into file. Current import-checker.py overlooks code fragment changed in this patch, because of a restriction below for a line starting code fragment. - filename must be specified before limit mark NG: cat <<EOF > FILE.py OK: cat > FILE.py <<EOF import-checker.py itself is fixed in subsequent patch.