Generate .coverage file

When I try to generate .coverage file(bench run-tests --coverage
) inside ./sites folder, I observe this:

Therefore, than I try to send this coverage file to travis-ci, I took this error:

emil@emil-UX430UNR ~/D/f/sites> coverage report -m
Couldn't read data from '/home/emil/Desktop/frappe-bench/sites/.coverage': UnicodeDecodeError: 'utf-8' codec can't decode byte 0xb0 in position 99: invalid start byte