Add cache for mypy (#27745)

* Add cache for mypy

* Update ruamel_yaml.py

azure-pipelines-ci.yml

@@ -172,13 +172,14 @@ stages:
       vmImage: 'ubuntu-latest'
     container: $[ variables['PythonMain'] ]
     steps:
-    - script: |
-        python -m venv venv
+    - template: templates/azp-step-cache.yaml@azure
+      parameters:
+        keyfile: 'requirements_test.txt | homeassistant/package_constraints.txt'
+        build: |
+          python -m venv venv
 
-        . venv/bin/activate
-        pip install -e .
-        pip install -r requirements_test.txt -c homeassistant/package_constraints.txt
-      displayName: 'Setup Env'
+          . venv/bin/activate
+          pip install -r requirements_test.txt -c homeassistant/package_constraints.txt
     - script: |
         . venv/bin/activate
         mypy homeassistant

homeassistant/util/ruamel_yaml.py

@@ -90,7 +90,7 @@ def load_yaml(fname: str, round_trip: bool = False) -> JSON_TYPE:
     if round_trip:
         yaml = YAML(typ="rt")
         # type ignore: https://bitbucket.org/ruamel/yaml/pull-requests/42
-        yaml.preserve_quotes = True  # type: ignore
+        yaml.preserve_quotes = True
     else:
         if ExtSafeConstructor.name is None:
             ExtSafeConstructor.name = fname