Revision 479833

shells/xonsh: Upgrade to version 0.7.8

Changelog: https://github.com/xonsh/xonsh/blob/0.7.8/CHANGELOG.rst

PR:		230369
Submitted by:	Roberto Fernandez Cueto <roberfern@gmail.com> (maintainer)
Reported by:	Nathan <ndowens@yahoo.com>
Reviewed by:	krion, mat
Reviewed by:	Nathan <ndowens@yahoo.com> (previous version)
Reviewed by:	John Hein <z7dr6ut7gs@snkmail.com> (previous version)
Approved by:	krion (mentor)
Differential Revision:	https://reviews.freebsd.org/D17152