copy_worksheet does not copy PageMargins
Created originally on Bitbucket by johnwoltman (John Woltman)
In version 2.6 (and, as of this report, 3.0) the copy_worksheet method does not include the PageMargins when copying. I would expect copying a worksheet to include copying the margins as well. I committed a fix at https://bitbucket.org/johnwoltman/openpyxl/commits/b944359cfec740a3f07858596d37747f8e7b1600 and can submit a pull request if it's wanted.