tests: make whitespace between functions and classes consistent

Mostly, this means two blank lines between classes and functions and one
line between methods. Since these checks are currently in preview, they
are done in a separate ruff invocation to avoid turning ALL the preview
checks on at the same time.

tests/util.py

@@ -31,6 +31,7 @@ log = logging.getLogger(__name__)
 
 REPLY_DATA = re.compile("<reply>[ \t\n\r]*<data[^<]*>(.*?)</data>", re.MULTILINE | re.DOTALL)
 
+
 class ClosingFileHandler(logging.StreamHandler):
     def __init__(self, filename):
         super(ClosingFileHandler, self).__init__()
@@ -59,6 +60,7 @@ class ClosingFileHandler(logging.StreamHandler):
                 self.release()
         return result
 
+
 class TestData:
     def __init__(self, data_folder):
         self.data_folder = data_folder
@@ -80,6 +82,7 @@ class TestData:
         # Left-strip the data so we do not get a newline before our data.
         return m.group(1).lstrip()
 
+
 if __name__ == '__main__':
     td = TestData("./data")
     data = td.get_test_data(1451)