devel/py-colorama: Fix build with Python 3.6

• Backport PR #294 [1] from upstream repository to enable default UTF-8 encoding in setup.py which fixes the build issue with Python 3.6.

PR: 252294, 251240 [2]
Submitted by: John W. O'Brien [1]
Reported by: Dani <i.dani@outlook.com> [2]
Reviewed by: koobs, ygy
Approved by: portmgr (blanket: build fix)