Support transactional-update for registration

On SUSE Micro systems with a RO root filesystem we need to use the
transactional-update register command to complete the registration.
SUSEConnect disables itself in this situation and produces and error.

Signed-off-by: Robert Schweikert <rjschwei@suse.com>

usr/sbin/registercloudguest

@@ -440,8 +440,41 @@ if not utils.is_registration_supported(cfg):
 
 # Check SUSE/SLES registration command to be present
 register_cmd = '/usr/sbin/SUSEConnect'
+# For transactional systems we need to do a few extra things
+p = subprocess.Popen(
+    ['findmnt', '--noheadings', '--json', '/'],
+    stdout=subprocess.PIPE,
+    stderr=subprocess.PIPE
+)
+res = p.communicate()
+# If we get an error from findmnt move forward on a best effort basis
+if p.returncode:
+    logging.warning('Unable to find filesystem information for "/"')
+else:
+    fsinfo = json.loads(res[0])
+    fsdata = fsinfo.get('filesystems')
+    if fsdata:
+        fsoptions = fsdata[0].get('options')
+        # If we are on a RO system we need to use the
+        # transactional-update command
+        if 'ro' in fsoptions.split(','):
+            cmd_name = 'transactional-update'
+            for path in ['/sbin/','/usr/sbin/']:
+                exec_path = path + cmd_name
+                if os.path.exists(exec_path):
+                   register_cmd = exec_path
+                   break
+            else:
+                err_msg = 'transactional-update command not found.'
+                err_msg += 'But is required on a RO filesystem for '
+                err_msg += 'registration'
+                logging.error(err_msg)
+                print(err_msg, file=sys.stderr)
+                sys.exit(1)
 if not (os.path.exists(register_cmd) and os.access(register_cmd, os.X_OK)):
-    logging.error('No registration executable found')
+    err_msg = 'No registration executable found'
+    logging.error(err_msg)
+    print(err_msg, file=sys.stderr)
     sys.exit(1)
 
 # get product list
@@ -460,8 +493,12 @@ failed_smts = []
 
 while not base_registered:
     utils.add_hosts_entry(registration_target)
+    sub_cmd = ''
+    if 'transactional' in register_cmd:
+        sub_cmd = 'register'
     cmd = [
         register_cmd,
+        sub_cmd,
         '--url',
         'https://%s' % registration_target.get_FQDN()
     ]