When in Python 3, then function `open` defaults to open the file in text mode
with and the encoding (if not passed) is taken from
`locale.getpreferredencoding`.
Using `getpreferredencoding` is not necessarily a good practice. Because
files might no be encoded that way.
When testing Odoo not in runbot (which has LANG set to C.UTF-8) you may get:
Traceback (most recent call last):
File "/home/gitlab-runner/src/odoo11/addons/web/tests/test_js.py", line 24, in test_check_suite
self._check_only_call('web.qunit_suite')
File "/home/gitlab-runner/src/odoo11/addons/web/tests/test_js.py", line 37, in _check_only_call
if RE_ONLY.search(fp.read()):
File "/home/gitlab-runner/virtualenvs/odoo11-MlnlRiTaP2/lib/python3.5/encodings/ascii.py", line 26, in decode
return codecs.ascii_decode(input, self.errors)[0]
UnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 4757: ordinal not in range(128)
The proposed solution is to read the file in binary mode, and decode to
unicode/str ourselves using utf-8. We don't use the encoding argument of
`open`, so that the code works in both Python 3 and Python 2.
PR #24434