util: add matching_dicts

Move some of this logic to a common util, so it can be used in
unittests.  The curtin version is close but expects to work on a storage
config, which is not a flat list.

subiquity/tests/api/test_api.py

@@ -28,7 +28,10 @@ from unittest.mock import patch
 from urllib.parse import unquote
 
 from subiquitycore.tests import SubiTestCase
-from subiquitycore.utils import astart_command
+from subiquitycore.utils import (
+    astart_command,
+    matching_dicts,
+    )
 
 default_timeout = 10
 
@@ -37,8 +40,7 @@ def match(items, **kw):
     typename = kw.pop('_type', None)
     if typename is not None:
         kw['$type'] = typename
-    return [item for item in items
-            if all(item.get(k) == v for k, v in kw.items())]
+    return matching_dicts(items, **kw)
 
 
 def timeout(multiplier=1):

subiquitycore/utils.py

@@ -176,3 +176,10 @@ def disable_subiquity():
                  "snap.subiquity.subiquity-service.service",
                  "serial-subiquity@*.service"])
     return
+
+
+def matching_dicts(items, **kw):
+    """Given an input sequence of dictionaries, return a list of dicts where
+    the supplied keyword arguments all match those items."""
+    return [item for item in items
+            if all(item.get(k) == v for k, v in kw.items())]