Error message with camera failure

[mdchia]

This error appears when attempting to run with a camera that is not responding.
Probably doesn't need to be fixed but documenting in case it gets common enough.

bvzlab@bvz-lab:~/sampling/cca$ python3 tissue-sampler.py actual-sampling
Read 2777 existing samples from output directory

Press enter to start sample capture, or 'exit' to exit...  
Traceback (most recent call last):
  File "tissue-sampler.py", line 189, in <module>
    Capturer(args['OUTDIR']).main()
  File "tissue-sampler.py", line 172, in main
    self.capture_sample()
  File "tissue-sampler.py", line 113, in capture_sample
    img = Image.open(io.BytesIO(img_jpg))
  File "/home/bvzlab/.local/lib/python3.5/site-packages/PIL/Image.py", line 2590, in open
    % (filename if filename else fp))
OSError: cannot identify image file <_io.BytesIO object at 0x7f35caa7cbf8>
bvzlab@bvz-lab:~/sampling/cca$ python3 tissue-sampler.py actual-sampling
Read 2778 existing samples from output directory

Press enter to start sample capture, or 'exit' to exit...  
Traceback (most recent call last):
  File "tissue-sampler.py", line 189, in <module>
    Capturer(args['OUTDIR']).main()
  File "tissue-sampler.py", line 172, in main
    self.capture_sample()
  File "tissue-sampler.py", line 113, in capture_sample
    img = Image.open(io.BytesIO(img_jpg))
  File "/home/bvzlab/.local/lib/python3.5/site-packages/PIL/Image.py", line 2590, in open
    % (filename if filename else fp))
OSError: cannot identify image file <_io.BytesIO object at 0x7efe3e462bf8>