skip optimization on error, don't exit process

[andreabisello]

optimizing a folder of images,
one of these image raise an error and entire process exits.
i suggest to keep optimization on other images.

this is the log

✅  [OPTIMIZED] ino-a-spirale-per-innaffiare-e-irrigare-piccole-superfici-forza-di-richiamo-diametro-9-mm-4647-202_.jpg
     JPG/RGB: 23.6 KB  ->  JPG/RGB: 19.4 KB 🔻 17.8%
✅  [OPTIMIZED] ino-a-spirale-per-innaffiare-e-irrigare-piccole-superfici-forza-di-richiamo-diametro-9-mm-4647-203_.jpg
     JPG/RGB: 40.1 KB  ->  JPG/RGB: 29.6 KB 🔻 26.2%concurrent.futures.process._RemoteTraceback:
"""
Traceback (most recent call last):
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\site-packages\PIL\JpegImagePlugin.py", line 628, in _save
    rawmode = RAWMODE[im.mode]
KeyError: 'P'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\concurrent\futures\process.py", line 239, in _process_worker
    r = call_item.fn(*call_item.args, **call_item.kwargs)
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\concurrent\futures\process.py", line 198, in _process_chunk
    return [fn(*args) for args in chunk]
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\concurrent\futures\process.py", line 198, in <listcomp>
    return [fn(*args) for args in chunk]
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\site-packages\optimize_images\__main__.py", line 67, in do_optimization
    return optimize_jpg(t)
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\site-packages\optimize_images\img_optimize_jpg.py", line 70, in optimize_jpg
    quality, jpgdiff = jpeg_dynamic_quality(img)
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\site-packages\optimize_images\img_dynamic_quality.py", line 93, in jpeg_dynamic_quality
    normalized_diff = get_diff_at_quality(photo, 95)
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\site-packages\optimize_images\img_dynamic_quality.py", line 52, in get_diff_at_quality
    photo.save(diff_photo, format="JPEG", quality=quality, progressive=True)
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\site-packages\PIL\Image.py", line 2088, in save
    save_handler(self, fp, filename)
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\site-packages\PIL\JpegImagePlugin.py", line 630, in _save
    raise IOError("cannot write mode %s as JPEG" % im.mode)
OSError: cannot write mode P as JPEG
"""

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "C:\Users\Andrea-Fisso\AppData\Local\Programs\Python\Python37-32\Scripts\optimize-images.exe\__main__.py", line 9, in <module>
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\site-packages\optimize_images\__main__.py", line 97, in main
    for r in executor.map(do_optimization, tasks):
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\concurrent\futures\process.py", line 483, in _chain_from_iterable_of_lists
    for element in iterable:
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\concurrent\futures\_base.py", line 598, in result_iterator
    yield fs.pop().result()
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\concurrent\futures\_base.py", line 428, in result
    return self.__get_result()
  File "c:\users\andrea-fisso\appdata\local\programs\python\python37-32\lib\concurrent\futures\_base.py", line 384, in __get_result
    raise self._exception
OSError: cannot write mode P as JPEG

[victordomingos]

@andreabisello I have been doing small changes that should have solved this issue. Please check out the current version on GitHub, which is slightly ahead of PyPI.

I am closing this issue for now, but in case there are still any problems please let me know.