Merge ~dbungert/curtin:log-source-handler into curtin:master

[Dan Bungert]

extract: log source information

If you try hard enough and follow mount commands backwards you can
surely get this same information, but when analyzing what the extract is
actually doing it's nice to just be able to see what the image stack is.

[Michael Hudson-Doyle (mwhudson)]

review: Approve

[Server Team CI bot (server-team-bot)]

PASSED: Continuous integration, rev:ca2c26453c4d5286b2a8b54d93c8e391c4c3e8c7
https://jenkins.canonical.com/server-team/job/curtin-ci/199/
Executed test runs:
    SUCCESS: https://jenkins.canonical.com/server-team/job/curtin-ci/nodes=metal-amd64/199/
    SUCCESS: https://jenkins.canonical.com/server-team/job/curtin-ci/nodes=metal-arm64/199/
    SUCCESS: https://jenkins.canonical.com/server-team/job/curtin-ci/nodes=metal-ppc64el/199/
    SUCCESS: https://jenkins.canonical.com/server-team/job/curtin-ci/nodes=metal-s390x/199/

Click here to trigger a rebuild:
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review: Approve (continuous-integration)

diff --git a/curtin/commands/extract.py b/curtin/commands/extract.py
index fc7749c..206790e 100644
--- a/curtin/commands/extract.py
+++ b/curtin/commands/extract.py
@@ -114,6 +114,7 @@ class LayeredSourceHandler(AbstractSourceHandler):
 
     def setup(self):
         self._tmpdir = tempfile.mkdtemp()
+        LOG.debug(f"Setting up Layered Source for stack {self.image_stack}")
         try:
             self._download()
             # Check that all images exists on disk and are not empty
@@ -158,6 +159,7 @@ class TrivialSourceHandler(AbstractSourceHandler):
         self.path = path
 
     def setup(self):
+        LOG.debug(f"Setting up Trivial Source for stack {self.path}")
         return self.path
 
     def cleanup(self):