Use sequence repetition instead of bytes constructor with integer argument.
diff --git a/Lib/pickletools.py b/Lib/pickletools.py
index 4eefc19..5e129b5 100644
--- a/Lib/pickletools.py
+++ b/Lib/pickletools.py
@@ -707,7 +707,7 @@
     >>> enc = s.encode('utf-8')
     >>> enc
     b'abcd\xea\xaf\x8d'
-    >>> n = bytes([len(enc)]) + bytes(7)  # little-endian 8-byte length
+    >>> n = bytes([len(enc)]) + b'\0' * 7  # little-endian 8-byte length
     >>> t = read_unicodestring8(io.BytesIO(n + enc + b'junk'))
     >>> s == t
     True