Merge pull request #1446 from rackerlabs/renovate/diskimage-builder-3.x

chore(deps): update dependency diskimage-builder to v3.40.0

Author: cardoe

ironic-images/requirements.txt

@@ -1,4 +1,4 @@
-diskimage-builder==3.39.0
+diskimage-builder==3.40.0
 ironic-python-agent-builder==6.1.0
 python-keystoneclient==5.7.0
 python-swiftclient==4.8.0