[dock][Host] Added logging on execution error of describe

beat/core/dock.py

@@ -173,6 +173,10 @@ class Host(object):
                 except Exception as e:
                     logger.warn("Ignoring potential environment at `%s' since " \
                             "`describe' output cannot be parsed: %s", image, str(e))
+            else:
+                logger.warn("Execution failed with status {}: \n"
+                            "stdout: '{}'\n"
+                            "stderr: '{}'".format(status, stdout, stderr))
             return {}