Continue from and log metadata reading errors on import

[damianmoore]

Issue #115 highlighted an exception happening in photos/utils/metadata.py when communicating with exiftool. This should be logged and not block the rest of the import process.

[damianmoore]

This situation has been improved as of 988a63b. Still need to put more effort and tests into this area.

[Red-F]

photonix | 2021-08-06 10:33:09,177 ERROR Error processing task: classify.face - 092e5cfe-0da0-45ad-91a3-7f5242d8f1d2 photonix | Traceback (most recent call last): photonix | File "/srv/photonix/photos/utils/classification.py", line 70, in __process_task photonix | self.runner(task.subject_id) photonix | File "/srv/photonix/classifiers/face/model.py", line 279, in run_on_photo photonix | x = (result['box'][0] + (result['box'][2] / 2)) / photo.base_file.width photonix | TypeError: unsupported operand type(s) for /: 'float' and 'NoneType'
This is an error caused by an earlier UnicodeDecodeError exception during metadata import from the photo. This causes All metadata attributes to be undefined but the 'MIME Type' attribute. Therefore photo.base_file.width returns NoneType causing the above exception when trying to divide.

The UnicodeDecodeError is thrown because of an invalid UTF-8 byte sequence in one of the metadata fields returned by the EXIFTOOL, in this case a 0xF8 which is not a valid start of an UTF-8 sequence.

PR #303 tries to solve this by adding the 'ignore' parameter to the decode call. This simply skips the invalid bytes, returning all metadata as expected. Strictly speaking of course at least on the attributes will not contain the data 'as it was' in the photo, but since that data is not readable anyway not much is lost.

In case ignoring the unicode errors causes the lines to be no longer syntactically correct with the 'text':'text' pattern, your above commit will catch that. This again may lead to an attribute being dropped, but is still much better than only returning the 'MIME Type' attribute.