examples/nanoterm.py: Handle OSError during os.read

[wngtk]

When running examples/nanoterm.py, I encountered the following error:

$ python3 examples/nanoterm.py ls
Traceback (most recent call last):
  File ".../pyte/examples/nanoterm.py", line 42, in <module>
    data = os.read(master_fd, 1024)
           ^^^^^^^^^^^^^^^^^^^^^^^^
OSError: [Errno 5] Input/output error

Similar to PR #171. We should also handle OSError exception.