I have problems trying to upload binary files in a form.

Declaration in the class:

data = fields.Binary()
....

Usage in the form:
<field name="data" />
<button name="import_file" string="Import" type="object" />

Normal files does upload as they should, but for example a Excel file gives this error:

UnicodeDecodeError: 'utf8' codec can't decode byte 0xd0 in position 110317: invalid continuation byte