Merge ~kwmonroe/layer-snap:master into ~stub/layer-snap:master

[Kevin W Monroe]

In fixing bug 1823293, we had to take special care to handle whitespace returned by snap.get:

https://git.launchpad.net/layer-snap/tree/lib/charms/layer/snap.py#n248

-----
sudo snap set core refresh.timer=''
...
>>> subprocess.check_output(['sudo', 'snap', 'get', 'core', 'refresh.timer']).decode('utf-8')
'\n'
-----

We *can* work around this by calling foo = snap.get().strip(), but I'm struggling to find a case where I'd want snap.get returning unstripped output. Hence, this MP strips output from the call to 'snap get'.

[Stuart Bishop (stub)]

Fine

review: Approve

diff --git a/lib/charms/layer/snap.py b/lib/charms/layer/snap.py
index 141ea1f..56b9bf8 100644
--- a/lib/charms/layer/snap.py
+++ b/lib/charms/layer/snap.py
@@ -235,8 +235,8 @@ def set_refresh_timer(timer=''):
 def get(snapname, key):
     '''Gets configuration options for a snap
 
-    This method returns the output that snapctl get command prints out.
-    This method will fail if snapname is not an installed snap
+    This method returns the stripped output from the snap get command.
+    This method will fail if snapname is not an installed snap.
     '''
     hookenv.log('Get config {} for snap {}'.format(key, snapname))
     if not reactive.is_flag_set(get_installed_flag(snapname)):
@@ -245,7 +245,7 @@ def get(snapname, key):
                 snapname), hookenv.WARNING)
         return
 
-    return subprocess.check_output(['snap', 'get', snapname, key])
+    return subprocess.check_output(['snap', 'get', snapname, key]).strip()
 
 def get_installed_version(snapname):
     '''Gets the installed version of a snapname.