master
Merge branch 'fix_39' of https://github.com/shadchin/python-future into shadchin-fix_39
Docs: replace http links with https
Merge https://github.com/fergofrog/python-future
add back in py2.6
Fix pow() with negative newint (issue #568)
Add PY37_PLUS, PY38_PLUS, and PY39_PLUS