try to work around Python quirk in main.py I/O support to avoid extraneous exceptions when reading piped stdin

[tomasohara]

Due to a quirk with Python, piped stdin filtered using head can lead to exceptions when reading stdin:

Traceback (most recent call last):
  File "/var/root/Mezcla/mezcla/convert_emoticons.py", line 157, in <module>
    main()
  File "/var/root/Mezcla/mezcla/convert_emoticons.py", line 150, in main
    print(ce.convert(line))
BrokenPipeError: [Errno 32] Broken pipe
Exception ignored in: <_io.TextIOWrapper name='<stdout>' mode='w' encoding='utf-8'>
BrokenPipeError: [Errno 32] Broken pipe

via convert_emoticons.py:

    for line in main_app.read_entire_input().splitlines():
        print(ce.convert(line))
    return

It would be good to add a workaround to main to avoid head scratching about client scripts.

See https://stackoverflow.com/questions/26692284/how-to-prevent-brokenpipeerror-when-doing-a-flush-in-python.