The Zuul upper-constraints env variable declaration needed
to be added to tox.ini otherwise an older constraints
was being used which does not work with newer
versions of python.
Adding legacy-resolver to attempt to resolve dependency
issues when importing different stx client modules.
Partial-Bug: #1997255
Signed-off-by: Al Bailey <al.bailey@windriver.com>
Change-Id: I88b779138aa3b19aca57e8f03f3c17ec077e7d58