Compute the dependency set for the python code being released and
report when the old minimum version no longer falls within the
specified range. For releases from master treat the message as an
error. For other branches treat the message as a warning.
Update clone_repo() to return the location where the clone was written
as a convenience to the caller.
Extract the logic for determining if a version is using
pre-versioning (alpha, beta, etc.) so it can be reused.
Change-Id: I22a2f6df7f3502e4fcbf2d61ef5fee849ab15529
Signed-off-by: Doug Hellmann <doug@doughellmann.com>