Merge lp:~seyeongkim/charm-helpers/fixing-filenotfounderror into lp:charm-helpers

[Seyeong Kim]

ignore FileNotFoundError when getting metadata file on the other machine's unit

related bug is https://bugs.launchpad.net/nrpe-charm/+bug/1712977

[Stuart Bishop (stub)]

FileNotFoundError doesn't exist with older Python releases. Its probably best to return None if 'not os.path.exists' rather than catch the exception.

review: Needs Fixing

[Stuart Bishop (stub)]

review: Approve

=== modified file 'charmhelpers/core/hookenv.py'
--- charmhelpers/core/hookenv.py	2017-08-10 14:31:31 +0000
+++ charmhelpers/core/hookenv.py	2017-08-28 14:14:31 +0000
@@ -218,6 +218,8 @@
         for rid in relation_ids(reltype):
             for unit in related_units(rid):
                 md = _metadata_unit(unit)
+                if not md:
+                    continue
                 subordinate = md.pop('subordinate', None)
                 if not subordinate:
                     return unit
@@ -511,7 +513,10 @@
     """
     basedir = os.sep.join(charm_dir().split(os.sep)[:-2])
     unitdir = 'unit-{}'.format(unit.replace(os.sep, '-'))
-    with open(os.path.join(basedir, unitdir, 'charm', 'metadata.yaml')) as md:
+    joineddir = os.path.join(basedir, unitdir, 'charm', 'metadata.yaml')
+    if not os.path.exists(joineddir):
+        return None
+    with open(joineddir) as md:
         return yaml.safe_load(md)