Merge ~yoshikadokawa/layer-snap:lp1938271 into layer-snap:master

[Yoshi Kadokawa]

Fix unexpected error when getting snap channel

LP: #1938271

Added extra try-exception layer to avoid unexpected errors.

[Yoshi Kadokawa (yoshikadokawa)]

It's been a week now, but would someone be able to review this?

[James Troup (elmo)]

LGTM

review: Approve

[Tom Haddon (mthaddon)]

One small comment inline, otherwise looks good.

[Tom Haddon (mthaddon)]

LGTM

review: Approve

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

This merge proposal is being monitored by mergebot. Change the status to Approved to merge.

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

Change successfully merged at revision d935a04074740e14feb0b73d485952b2546ae04c

diff --git a/lib/charms/layer/snap.py b/lib/charms/layer/snap.py
index 6909748..06cc4b1 100644
--- a/lib/charms/layer/snap.py
+++ b/lib/charms/layer/snap.py
@@ -300,7 +300,15 @@ def get_installed_channel(snapname):
             hookenv.WARNING,
         )
         return
-    return subprocess.check_output(cmd).decode("utf-8", errors="replace").partition("tracking:")[-1].split()[0]
+    try:
+        return subprocess.check_output(cmd).decode("utf-8", errors="replace").partition("tracking:")[-1].split()[0]
+    except Exception as e:
+        # If it fails to get the channel information(ex. installed via resource), return nothing.
+        hookenv.log(
+            "Cannot get snap tracking (channel): {}".format(e),
+            hookenv.WARNING,
+        )
+        return
 
 
 def _snap_args(