Fix DeprecationWarning: invalid escape sequence

[devtools/testlib] avoid hidding AttributeError in create_user() commit() might raise a AttributeError too. Use getattr(req, 'cnx', req) instead, which is a form already used to get the real cnx in some code: cubicweb/rset.py:577: cnx = getattr(self.req, 'cnx', self.req) cubicweb/schema.py:353: with getattr(_cw, 'cnx', _cw).security_enabled(read=False): We could use if hasattr(req, 'commit') here too but it lead to 3 additionals lines. Maybe we should have commit() and rollback() on cubicweb.web.request.ConnectionCubicWebRequestBase too ?

Fix DeprecationWarning: invalid escape sequence \

DeprecationWarning: The 'warn' method is deprecated, use 'warning' instead

[mod] remove backward compatible code for passlib and force modern version

DeprecationWarning: Please use assertEqual instead.

DeprecationWarning: Please use assertRaisesRegex instead.

DeprecationWarning: inspect.getargspec() is deprecated since Python 3.0, use inspect.signature() or inspect.getfullargspec()

[README] add testing instructions

Add pytest-subtests to dev requirements This pytest plugin adds support for unittest's TestCase.subTest (for Python >= 3.4). Since we we now only support python3 and since we use a fair amount of these, let's benefit of better reporting by using this plugin.

[test] use unittest.mock instead of mock library Now that we use Python 3 only, this is possible.

Drop python2 support This mostly consists in removing the dependency on "six" and updating the code to use only Python3 idioms. Notice that we previously used TemporaryDirectory from cubicweb.devtools.testlib for compatibility with Python2. We now directly import it from tempfile.

Merge with 3.26

Remove unused imports in cubicweb.pyramid.config