Use contextmanager for all file-like objects which don't have __exit__ ; remove duplicate import.
Use contextmanager for all file-like objects which don't have __exit__ ; remove duplicate import.

rs/petl,rs/petl,rs/petl,psnj/petl,Marketing1by1/petl,alimanfoo/petl,thatneat/petl,obsoleter/petl,obsoleter/petl,obsoleter/petl