Obfuscated logging in external preprocessing

[jwindhager]

The following lines should be changed to include the original exception potentially raised here:

steinbock/steinbock/preprocessing/external.py

Lines 83 to 84 in bc10207

	except Exception:
	logger.warning(f"Unsupported file format: {ext_img_file}")

For example similar to the following lines:

steinbock/steinbock/measurement/intensities.py

Lines 65 to 66 in bc10207

	except Exception as e:
	logger.exception(f"Error measuring intensities in {img_file}: {e}")