Use UTC for test_query_with_creation_date comparisons

The creation time of the record inserted by upsert_sample() will
be reported in UTC, so we need to compare against today in UTC.
Otherwise tests fail when run locally before lunchtimeish as it
is still "yesterday" in UTC, so lt=today unexpectedly returns
the just-created record.

test/test_sequencing_groups.py

@@ -1,4 +1,4 @@
-from datetime import date
+from datetime import datetime
 from test.testbase import DbIsolatedTest, run_as_sync
 
 from db.python.layers import AnalysisLayer, SampleLayer, SequencingGroupLayer
@@ -202,31 +202,34 @@ async def test_query_with_creation_date(self):
         sample_to_insert = get_sample_model()
         await self.slayer.upsert_sample(sample_to_insert)
 
+        # There's a race condition here -- don't run this near UTC midnight!
+        today = datetime.utcnow().date()
+
         # Query for sequencing group with creation date before today
         sgs = await self.sglayer.query(
-            SequencingGroupFilter(created_on=GenericFilter(lt=date.today()))
+            SequencingGroupFilter(created_on=GenericFilter(lt=today))
         )
         self.assertEqual(len(sgs), 0)
 
         # Query for sequencing group with creation date today
         sgs = await self.sglayer.query(
-            SequencingGroupFilter(created_on=GenericFilter(eq=date.today()))
+            SequencingGroupFilter(created_on=GenericFilter(eq=today))
         )
         self.assertEqual(len(sgs), 1)
 
         sgs = await self.sglayer.query(
-            SequencingGroupFilter(created_on=GenericFilter(lte=date.today()))
+            SequencingGroupFilter(created_on=GenericFilter(lte=today))
         )
         self.assertEqual(len(sgs), 1)
 
         sgs = await self.sglayer.query(
-            SequencingGroupFilter(created_on=GenericFilter(gte=date.today()))
+            SequencingGroupFilter(created_on=GenericFilter(gte=today))
         )
         self.assertEqual(len(sgs), 1)
 
         # Query for sequencing group with creation date today
         sgs = await self.sglayer.query(
-            SequencingGroupFilter(created_on=GenericFilter(gt=date.today()))
+            SequencingGroupFilter(created_on=GenericFilter(gt=today))
         )
         self.assertEqual(len(sgs), 0)