Bulk scan dies when one process raises an uncaught exception

[krayzpipes]

When a subprocess throws an uncaught exception, the entire bulk scan stops instead of just skipping and letting the others finish.

Traceback (most recent call last):
  File "/usr/lib64/python3.6/multiprocessing/pool.py", line 119, in worker
    result = (True, func(*args, **kwds))
  File "/usr/lib64/python3.6/multiprocessing/pool.py", line 44, in mapstar
    return list(map(*args))
  File "/home/some_user/venv/lib64/python3.6/site-packages/txtferret/cli.py", line 69, in bootstrap
    ferret.scan_file()
  File "/home/some_user/venv/lib64/python3.6/site-packages/txtferret/core.py", line 315, in scan_file
    for index, line in enumerate(rf):
  File "/usr/lib64/python3.6/codecs.py", line 321, in decode
    (result, consumed) = self._buffer_decode(data, self.errors, final)
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe1 in position 1471: invalid continuation byte
"""

Traceback (most recent call last):
  File "/home/some_user/venv/bin/txtferret", line 11, in <module>
    sys.exit(main())
  File "/home/some_user/venv/lib64/python3.6/site-packages/txtferret/__init__.py", line 7, in main
    exit(cli())
  File "/home/some_user/venv/lib64/python3.6/site-packages/click/core.py", line 764, in __call__
    return self.main(*args, **kwargs)
  File "/home/some_user/venv/lib64/python3.6/site-packages/click/core.py", line 717, in main
    rv = self.invoke(ctx)
  File "/home/some_user/venv/lib64/python3.6/site-packages/click/core.py", line 1137, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/some_user/venv/lib64/python3.6/site-packages/click/core.py", line 956, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/some_user/venv/lib64/python3.6/site-packages/click/core.py", line 555, in invoke
    return callback(*args, **kwargs)
  File "/home/some_user/venv/lib64/python3.6/site-packages/txtferret/cli.py", line 190, in scan
    results = p.map(bootstrap, configs)
  File "/usr/lib64/python3.6/multiprocessing/pool.py", line 266, in map
    return self._map_async(func, iterable, mapstar, chunksize).get()
  File "/usr/lib64/python3.6/multiprocessing/pool.py", line 644, in get
    raise self._value
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xe1 in position 1471: invalid continuation byte

Need to fix the UnicodeDecoding issues in another issue.

[krayzpipes]

Codec / encoding support addressed in Issue #26