Add a log message around import failures.

Since the import failure can be an expected failure do not log that
failure at a WARNING level, but to start log it at a DEBUG level. This
will help in figuring out why imports fail (if they ever do) for developer
and cloud-init users. Previously it is hard to know if a module fails
importing for a valid reason (not existent) or an invalid reason (the
module exists but the module has a dependency which is not satisfied).

2 files changed, 5 insertions, 2 deletions

diff --git a/ChangeLog b/ChangeLog
index 8113da9c..e39cf0ca 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,6 @@
 0.7.5:
  - open 0.7.5
+ - Add a debug log message around import failures
 0.7.4:
  - fix issue mounting 'ephemeral0' if ephemeral0 was an alias for a
    partitioned block device with target filesystem on ephemeral0.1.
diff --git a/cloudinit/importer.py b/cloudinit/importer.py
index 71cf2726..a094141a 100644
--- a/cloudinit/importer.py
+++ b/cloudinit/importer.py
@@ -36,6 +36,7 @@ def find_module(base_name, search_paths, required_attrs=None):
     found_places = []
     if not required_attrs:
         required_attrs = []
+    # NOTE(harlowja): translate the search paths to include the base name.
     real_paths = []
     for path in search_paths:
         real_path = []
@@ -50,8 +51,9 @@ def find_module(base_name, search_paths, required_attrs=None):
         mod = None
         try:
             mod = import_module(full_path)
-        except ImportError:
-            pass
+        except ImportError as e:
+            LOG.debug("Failed at attempted import of '%s' due to: %s",
+                      full_path, e)
         if not mod:
             continue
         found_attrs = 0