This requires an external program and only works on Debian hosts.
Newer versions of exim (4.91) have SPF functionality built-in, but
they are not yet available to us.
Change-Id: Idfe6bfa5a404b61c8761aa1bfa2212e4b4e32be9
This is used in a handler which may be run after intervening roles;
ensure it has a unique variable name.
Change-Id: I6a3d856d3252ff62220d9769232e31ea7c4f9080
Move the exim role to be a "generic" role in the top-level roles/
directory, making it available for use as a Zuul role.
Update the linters jobs to look for roles in the top level
Update the Role documentation to explain what the split in roles is
about.
Change-Id: I6b49d2a4b120141b3c99f5f1e28c410da12d9dc3