Update error logging

In case of tarball extraction failures, log the exception and stack
trace. These exceptions could cause the host to become stuck. The stack
trace can help with debugging.

deploy-agent/deployd/download/downloader.py

@@ -121,13 +121,13 @@ def download(self):
             log.info("Successfully extracted {} to {}".format(local_full_fn, working_dir))
         except tarfile.TarError as e:
             status = Status.FAILED
-            log.error("Failed to extract files: {}".format(e))
+            log.exception("Failed to extract tar files")
         except OSError as e:
             status = Status.FAILED
-            log.error("Failed: {}".format(e))
+            log.exception("Failed to extract files. OSError:")
         except Exception:
             status = Status.FAILED
-            log.error(traceback.format_exc())
+            log.exception("Failed to extract files")
         finally:
             return status