Example:

$ python2 -c 'import sys, marshal; marshal.dump(1234567890, sys.stdout)' | python3 -c 'import sys, marshal; print(marshal.load(sys.stdin.buffer))'
1234567890

$ python2 -c 'import sys, marshal; marshal.dump(123456789012345, sys.stdout)' | python3 -c 'import sys, marshal; print(marshal.load(sys.stdin.buffer))'
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ValueError: bad marshal data (unknown type code)

 python2 -c 'import sys, marshal; marshal.dump(12345678901234567890, sys.stdout)' | python3 -c 'import sys, marshal; print(marshal.load(sys.stdin.buffer))'
12345678901234567890

PR 4381 reverts this change and simplifies the restored code.