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.
[workspace]
members = ["hgcli"]
exclude = ["chg"]