Fix Python sqlite3 converter/adapter deprecation warning

gyb.py

@@ -1960,6 +1960,30 @@ def message_hygiene(msg):
     return omsg.as_bytes()
 
 
+def adapt_date_iso(val):
+    """Adapt datetime.date to ISO 8601 date."""
+    return val.isoformat()
+
+def adapt_datetime_iso(val):
+    """Adapt datetime.datetime to timezone-naive ISO 8601 date."""
+    return val.isoformat()
+
+def adapt_datetime_epoch(val):
+    """Adapt datetime.datetime to Unix timestamp."""
+    return int(val.timestamp())
+
+def convert_date(val):
+    """Convert ISO 8601 date to datetime.date object."""
+    return datetime.date.fromisoformat(val.decode())
+
+def convert_datetime(val):
+    """Convert ISO 8601 datetime to datetime.datetime object."""
+    return datetime.datetime.fromisoformat(val.decode())
+
+def convert_timestamp(val):
+    """Convert Unix epoch timestamp to datetime.datetime object."""
+    return datetime.datetime.fromtimestamp(int(val))
+
 def main(argv):
   global options, gmail
   options = SetupOptionParser(argv)
@@ -2034,6 +2058,12 @@ def main(argv):
       print("\nUsing backup folder %s" % options.local_folder)
       global sqlconn
       global sqlcur
+      sqlite3.register_adapter(datetime.date, adapt_date_iso)
+      sqlite3.register_adapter(datetime.datetime, adapt_datetime_iso)
+      sqlite3.register_adapter(datetime.datetime, adapt_datetime_epoch)
+      sqlite3.register_converter("date", convert_date)
+      sqlite3.register_converter("datetime", convert_datetime)
+      sqlite3.register_converter("timestamp", convert_timestamp)
       sqlconn = sqlite3.connect(sqldbfile,
         detect_types=sqlite3.PARSE_DECLTYPES)
       sqlcur = sqlconn.cursor()