remove unneeded re import
pylinting, better log messages, docstrings, no logic changes
correctly check for verify_master_pub_sign when no key accepted before
CentOS 7 and Scientific Linux 7 should also use systemd module
set sensible default values to ease configuration

signing key-pair settings
master_sign_key_name - name of the signing key-pair, without suffix
master_sign_pubkey - enable/disable signing the public key

signing signature settings
master_pubkey_signature - the pre-computed signature of master.pub + <sign_key>.pem
master_use_pubkey_signature - enable/disable usage of the pre-computed signature

verify_master_pub_sig - enable pubkey signature checking on the minion
switch between signing with own key-pair of usage of pre-computed signature only

if signing the pubkey is enabled, the master will switch between signing the pubkey
on the fly or just adding the pre-computed pubkeys signature to the reply.
if not already present, auto-generate a signing key-pair or use pre-computed signature

if signing the pubkey is enabled, the master will either generate a new signing key-pair
on the fly (if none is found) or use the pre-computed pubkey-signature. if the pre-computed
signature is enabled but not present, the master will complain and exit.
Merge pull request #13748 from simoncadman/develop

CentOS 7 and Scientific Linux 7 should also use systemd module
Fixing pylint violations
Update expected message
Add sock_dir to raet swarming
Add worker sleep betwen creation
Merge pull request #13764 from pass-by-value/more_test_fixes

Update expected message
clarifications to gce cloud docs
iraet swarm needs ports
Merge pull request #13765 from rallytime/gce_docs

clarifications to gce cloud docs
Merge pull request #13763 from nmadhok/fix-lint

Fixing pylint violations
Fixes the problem where service module is unavailable on RedHat, CentOs and Scientific Linux
Fixing merge conflict
Fixing merge conflicts