Fail test if tool writes to input dir

[bernt-matthias]

Would be nice if planemo test would fail for such cases automatically. Like so galaxyproject/tools-iuc#3986 (comment)

[bernt-matthias]

Alternatively we could do the following in the CI:

FILE_PATH=$(mktemp -d)
planemo test --file_path $FILEPATH ...

WROTE=$(find $FILE_PATH -type f \( ! -name "*.dat" ! -name "dataset_.*_files" \))

if [[ $WROTE ]]; then
    >&2 echo "tool wrote files into Galaxy's file dir: "
    >&2 echo $WROTE
    exit 1
fi

[bernt-matthias]

Closing this, since containerized testing allows to do this. Still I leave #1190 open, because it might have value .. but others need to judge this.