Merge ~barryprice/charm-canonical-livepatch/+git/canonical-livepatch-charm:master into ~livepatch-charmers/charm-canonical-livepatch:master

[Barry Price]

diff --git a/files/check_canonical-livepatch.py b/files/check_canonical-livepatch.py
index 3953661..27c9f69 100644
--- a/files/check_canonical-livepatch.py
+++ b/files/check_canonical-livepatch.py
@@ -4,7 +4,7 @@
 
 import os
 import nagios_plugin
-from subprocess import check_call, check_output
+from subprocess import check_output
 
 
 ################################################################################
@@ -12,7 +12,7 @@ from subprocess import check_call, check_output
 def check_package_installed():
     cmd = ['snap', 'list', 'canonical-livepatch']
     try:
-        res = check_output(cmd, universal_newlines=True)
+        check_output(cmd, universal_newlines=True)
     except:
         raise nagios_plugin.CriticalError("canonical-livepatch snap is not installed")
 
diff --git a/reactive/canonical_livepatch.py b/reactive/canonical_livepatch.py
index ce47d43..102df07 100644
--- a/reactive/canonical_livepatch.py
+++ b/reactive/canonical_livepatch.py
@@ -149,14 +149,14 @@ def update_key():
         cmd = ['/snap/bin/canonical-livepatch', 'disable']
         hookenv.log('Disabling canonical-livepatch ahead of key change to work around LP#1628823')
         try:
-            __ = check_output(cmd, universal_newlines=True)
+            check_output(cmd, universal_newlines=True)
         except CalledProcessError as e:
             hookenv.log('Unable to deactivate: {}'.format(str(e)))
 
         cmd = ['/snap/bin/canonical-livepatch', 'enable', '{}'.format(livepatch_key.strip())]
         hookenv.log('Activating canonical-livepatch with your key')
         try:
-            __ = check_output(cmd, universal_newlines=True)
+            check_output(cmd, universal_newlines=True)
         except CalledProcessError as e:
             hookenv.log('Unable to activate: {}'.format(str(e)))
             hookenv.status_set('blocked', 'Activation failed')
@@ -212,10 +212,12 @@ def init_nagios_checks(nagios):
         'files/check_canonical-livepatch.py',
         '/usr/lib/nagios/plugins/check_canonical-livepatch.py',
     )
-    file_to_units(
-        'files/canonical-livepatch-status.txt',
-        '/var/lib/nagios/canonical-livepatch-status.txt',
-    )
+    # don't overwrite an existing status file
+    if not path.exists('/var/lib/nagios/canonical-livepatch-status.txt'):
+        file_to_units(
+            'files/canonical-livepatch-status.txt',
+            '/var/lib/nagios/canonical-livepatch-status.txt',
+        )
 
     # use the interface to create the check
     nagios.add_check(["/usr/lib/nagios/plugins/check_canonical-livepatch.py", ],