tree e100c75f85b4763df7a9d28c543336a93d5ab324
parent 61ffae7d1628f0551e77e1a2853209ff24c1f1bb
author wangzihao <wangzihao@yovole.com> 1621490991 +0800
committer Michael Johnson <johnsomor@gmail.com> 1645133477 +0000

Use TOX_CONSTRAINTS_FILE and update tox

UPPER_CONSTRAINTS_FILE is old name and deprecated
This allows to use upper-constraints file as more
readable way instead of UPPER_CONSTRAINTS_FILE=<lower-constraints file>.

bumps min version of tox to 3.18.0 in order to replace tox's
whitelist_externals by allowlist_externals option:
https://github.com/tox-dev/tox/blob/master/docs/changelog.rst#v3180-2020-07-23

Change-Id: I4b14b7882fd6806c864d5ac0445e45df450dc218