I've found the problem that gave an error in the ocr : in the apps/ocr/conf/settings.py the path to tesseract was pointing a wrong folder /usr/bin instead of /usr/local/bin
{'name': u'TESSERACT_PATH', 'global_name': u'OCR_TESSERACT_PATH',
'default': u'/usr/local/bin/tesseract', 'exists': True},
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