Apply suggestions from code review

Co-authored-by: Victor Stinner <vstinner@python.org>

Author: marcelm

Lib/test/test_memoryio.py

@@ -520,12 +520,12 @@ def test_relative_seek(self):
     def test_peek(self):
         buf = self.buftype("1234567890")
         memio = self.ioclass(buf)
-        pos = memio.tell()
+        self.assertEqual(memio.tell(), 0)
         self.assertEqual(memio.peek(1), buf[:1])
         self.assertEqual(memio.peek(1), buf[:1])
         self.assertEqual(memio.peek(), buf[:1])
         self.assertEqual(memio.peek(0), buf)
-        self.assertEqual(memio.tell(), pos)
+        self.assertEqual(memio.tell(), 0)
         memio.read(1)
         self.assertEqual(memio.peek(1), buf[1:2])
         self.assertEqual(memio.peek(), buf[1:2])