Refactor session db logging and key generation for sessions/otks While I was working on the redis sessiondb stuff, I noticed that log_wanrning, get_logger ... was duplicated. Also there was code to generate a unique key for otks that was duplicated. Changes: creating new sessions_common.py and SessionsCommon class to provide methods: log_warning, log_info, log_debug, get_logger, getUniqueKey getUniqueKey method is closer to the method used to make session keys in client.py. sessions_common.py now report when random_.py chooses a weak random number generator. Removed same from rest.py. get_logger reconciles all logging under roundup.hyperdb.backends.<name of BasicDatabase class> some backends used to log to root logger. have BasicDatabase in other sessions_*.py modules inherit from SessionCommon. change logging to use log_* methods. In addition: remove unused imports reported by flake8 and other formatting changes modify actions.py, rest.py, templating.py to use getUniqueKey method. add tests for new methods test_redis_session.py swap out ModuleNotFoundError for ImportError to prevent crash in python2 when redis is not present. allow injection of username:password or just password into redis connection URL. set pytest_redis_pw envirnment variable to password or user:password when running test.

"""
In Python 3, sometimes TAL "python:" expressions that refer to
variables but not all variables are recognized. That is in Python 2.7
all variables used in a TAL "python:" expression are recognized as
references. In Python 3.5 (perhaps earlier), some TAL "python:"
expressions refer to variables but the reference generates an error
like this:

<class 'NameError'>: name 'some_tal_variable' is not defined

even when the variable is defined. Output after this message lists the
variable and its value.
"""

import unittest

from roundup.cgi.PageTemplates.PythonExpr import PythonExpr as PythonExprClass

class ExprTest(unittest.TestCase):
    def testExpr(self):
        expr = '[x for x in context.assignedto ' \
               'if x.realname not in user_realnames]'
        pe = PythonExprClass('test', expr, None)
        # Looking at the expression, only context and user_realnames are
        # external variables. The names assignedto and realname are members,
        # and x is local.
        required_names = ['context', 'user_realnames']
        got_names = pe._f_varnames
        for required_name in required_names:
            self.assertIn(required_name, got_names)