tools: fix AttributeError: __exit__ on Python 2.6

Error occurs while dealing with Tar archives

PR-URL: https://github.com/nodejs/node/pull/17663


Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Steven R Loomis <srloomis@us.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>