anchor.diff:  
     mkPython =
       { name
  +    , dirname
       , version
       , src
       , python
  
positive.code:   mkBackend =
      args @
      { name
      , version
      , src
      , python
  
negative.code:           # generate MANIFEST.in to make sure every file is included
            rm -f MANIFEST.in
            cat > MANIFEST.in <<EOF
            recursive-include ${dirname}/*
  
            include VERSION
            include ${dirname}/*.ini
            include ${dirname}/*.json
            include ${dirname}/*.mako
            include ${dirname}/*.yml
  
            recursive-exclude * __pycache__
            recursive-exclude * *.py[co]
  