diff --git a/Makefile b/Makefile
index 9b681b2e..464dcf58 100644
--- a/Makefile
+++ b/Makefile
@@ -5,7 +5,7 @@ upgrade:
 	fab upgrade
 
 db:
-	@python ./fabfile/db.py > global/overlay/etc/puppet/cosmos-db.yaml
+	@python3 ./fabfile/db.py > global/overlay/etc/puppet/cosmos-db.yaml
 	@git add global/overlay/etc/puppet/cosmos-db.yaml && git commit -m "update db" global/overlay/etc/puppet/cosmos-db.yaml
 
 tag: db
diff --git a/fabfile/db.py b/fabfile/db.py
index 081764dd..7f21ed51 100644
--- a/fabfile/db.py
+++ b/fabfile/db.py
@@ -1,49 +1,63 @@
 import os
+import sys
 import yaml
 import re
 
+# disallow python2 as the output will not be correct
+if sys.version_info.major != 3:
+    sys.stderr.write('python2 no longer supported\n')
+    sys.exit(1)
+
+
 def _all_hosts():
-   return filter(lambda fn: '.' in fn and not fn.startswith('.') and os.path.isdir(fn),os.listdir("."))
+    return list(filter(lambda fn: '.' in fn and not fn.startswith('.') and os.path.isdir(fn), os.listdir(".")))
+
 
 def _load_db():
-   rules = dict()
-   rules_file = "cosmos-rules.yaml";
-   if os.path.exists(rules_file):
-      with open(rules_file) as fd:
-         rules.update(yaml.load(fd))
- 
-   all_hosts = _all_hosts()
+    rules_file = "cosmos-rules.yaml"
+    if not os.path.exists(rules_file):
+        sys.stderr.write('%s not found'.format(rules_file))
+        sys.exit(1)
 
-   members = dict()
-   for node_name in all_hosts:
-      for reg,cls in rules.iteritems():
-         if re.search(reg,node_name):
-            for cls_name in cls.keys():
-               h = members.get(cls_name,[])
-               h.append(node_name)
-               members[cls_name] = h
-   members['all'] = all_hosts
+    with open(rules_file) as fd:
+        rules = yaml.load(fd, Loader=yaml.SafeLoader)
 
-   classes = dict()
-   for node_name in all_hosts:
-      node_classes = dict()
-      for reg,cls in rules.iteritems():
-         if re.search(reg,node_name):
-            node_classes.update(cls)
-      classes[node_name] = node_classes
+    all_hosts = _all_hosts()
 
-   # Sort member lists for a more easy to read diff
-   for cls in members.keys():
-       members[cls].sort()
+    members = dict()
+    for node_name in all_hosts:
+        for reg, cls in rules.items():
+            if re.match(reg, node_name):
+                for cls_name in cls.keys():
+                    h = members.get(cls_name, [])
+                    h.append(node_name)
+                    members[cls_name] = h
+    members['all'] = all_hosts
+
+    classes = dict()
+    for node_name in all_hosts:
+        node_classes = dict()
+        for reg, cls in rules.items():
+            if re.match(reg, node_name):
+                node_classes.update(cls)
+        classes[node_name] = node_classes
+
+    # Sort member lists for a more easy to read diff
+    for cls in members.keys():
+        members[cls].sort()
+
+    return dict(classes=classes, members=members)
 
-   return dict(classes=classes,members=members)
 
 _db = None
+
+
 def cosmos_db():
-   global _db
-   if _db is None:
-      _db = _load_db()
-   return _db
+    global _db
+    if _db is None:
+        _db = _load_db()
+    return _db
+
 
 if __name__ == '__main__':
-   print yaml.dump(cosmos_db())
+    print(yaml.dump(cosmos_db(), default_flow_style=None))