NixOS
diff --git a/.travis.yml b/.travis.yml
@@ -2,6 +2,7 @@ language: nix
 before_script:
   - sudo echo 'sandbox = true' | sudo tee /etc/nix/nix.conf
 script:
-  - nix-shell -p python3Packages.black --run "black . --check --diff"
+  - nix-shell --run "mypy nixops"
+  - nix-shell --run "black . --check --diff"
   - ./dev-shell --run "./coverage-tests.py -a '!libvirtd,!gce,!ec2,!azure' -v"
-  - nix-build --quiet release.nix -A build.x86_64-linux -I nixpkgs=channel:nixos-19.03
+  - nix-build --quiet release.nix -A build.x86_64-linux -I nixpkgs=channel:nixos-19.09
diff --git a/maintainers/dump-route53-hosted-zone.py b/maintainers/dump-route53-hosted-zone.py
@@ -19,13 +19,11 @@
 by_hostname = {}
 for record in records:
     name = record["Name"]
-    if not name in by_hostname:
+    if name not in by_hostname:
         by_hostname[name] = []
     by_hostname[name].append(record)
 
-count = {
-    k: len([x for x in v if x["Type"] == "A"]) for (k, v) in list(by_hostname.items())
-}
+count = {k: sum(1 for x in v if x["Type"] == "A") for (k, v) in by_hostname.items()}
 
 
 def print_record(record):
@@ -93,6 +91,7 @@ def print_record(record):
     )
 )
 print("  resources.route53RecordSets = {")
-list(map(print_record, records))
+for record in records:
+    print_record(record)
 print("  };")
 print("}")
diff --git a/nixops/ansi.py b/nixops/ansi.py
@@ -0,0 +1,17 @@
+import sys
+
+
+def ansi_highlight(s: str, outfile=sys.stderr) -> str:
+    return "\033[1;35m" + s + "\033[0m" if outfile.isatty() else s
+
+
+def ansi_warn(s: str, outfile=sys.stderr) -> str:
+    return "\033[1;33m" + s + "\033[0m" if outfile.isatty() else s
+
+
+def ansi_error(s: str, outfile=sys.stderr) -> str:
+    return "\033[1;31m" + s + "\033[0m" if outfile.isatty() else s
+
+
+def ansi_success(s: str, outfile=sys.stderr) -> str:
+    return "\033[1;32m" + s + "\033[0m" if outfile.isatty() else s
diff --git a/nixops/backends/__init__.py b/nixops/backends/__init__.py
@@ -3,7 +3,7 @@
 import os
 import re
 import subprocess
-
+from typing import Dict, Any
 import nixops.util
 import nixops.resources
 import nixops.ssh_util
@@ -208,6 +208,10 @@ def remove_backup(self, backup_id, keep_physical=False):
             "don't know how to remove a backup for machine ‘{0}’".format(self.name)
         )
 
+    def get_backups(self) -> Dict[str, Dict[str, Any]]:
+        self.warn("don't know how to list backups for ‘{0}’".format(self.name))
+        return {}
+
     def backup(self, defn, backup_id):
         """Make backup of persistent disks, if possible."""
         self.warn(
@@ -263,7 +267,7 @@ def send_keys(self):
             return
         if self.store_keys_on_machine:
             return
-        for k, opts in list(self.get_keys().items()):
+        for k, opts in self.get_keys().items():
             self.log("uploading key ‘{0}’...".format(k))
             tmp = self.depl.tempdir + "/key-" + self.name
             if "destDir" not in opts: