Migration Django 1.10 a 1.11 Error environment can only contain strings

Recently I actulize django from its version 1.10 to 1.11 and the console sends me the following error

    Traceback (most recent call last):
  File "manage.py", line 10, in <module>
    execute_from_command_line(sys.argv)
  File "C:\Users\nbueno\Envs\nworksdev\lib\site-packages\django\core\management\__init__.py", line 363, in execute_from_command_line
    utility.execute()
  File "C:\Users\nbueno\Envs\nworksdev\lib\site-packages\django\core\management\__init__.py", line 355, in execute
    self.fetch_command(subcommand).run_from_argv(self.argv)
  File "C:\Users\nbueno\Envs\nworksdev\lib\site-packages\django\core\management\base.py", line 283, in run_from_argv
    self.execute(*args, **cmd_options)
  File "C:\Users\nbueno\Envs\nworksdev\lib\site-packages\django\core\management\commands\runserver.py", line 62, in execute
    super(Command, self).execute(*args, **options)
  File "C:\Users\nbueno\Envs\nworksdev\lib\site-packages\django\core\management\base.py", line 330, in execute
    output = self.handle(*args, **options)
  File "C:\Users\nbueno\Envs\nworksdev\lib\site-packages\django\core\management\commands\runserver.py", line 101, in handle
    self.run(**options)
  File "C:\Users\nbueno\Envs\nworksdev\lib\site-packages\django\core\management\commands\runserver.py", line 110, in run
    autoreload.main(self.inner_run, None, options)
  File "C:\Users\nbueno\Envs\nworksdev\lib\site-packages\django\utils\autoreload.py", line 332, in main
    reloader(wrapped_main_func, args, kwargs)
  File "C:\Users\nbueno\Envs\nworksdev\lib\site-packages\django\utils\autoreload.py", line 303, in python_reloader
    exit_code = restart_with_reloader()
  File "C:\Users\nbueno\Envs\nworksdev\lib\site-packages\django\utils\autoreload.py", line 289, in restart_with_reloader
    exit_code = subprocess.call(args, env=new_environ)
  File "c:\python27\Lib\subprocess.py", line 523, in call
    return Popen(*popenargs, **kwargs).wait()
  File "c:\python27\Lib\subprocess.py", line 711, in __init__
    errread, errwrite)
  File "c:\python27\Lib\subprocess.py", line 959, in _execute_child
    startupinfo)
TypeError: environment can only contain strings

Apparently this simply exists when the operating system platform is windows because in Linux the error does not exist, but I can not identify if the problem lies in the same django or in the python 2.7 when loading variables "environment "

Try to replicate the project from 0 in django 1.11 and apparently I get the same error when I change database, I use an oracle database and the cx_oracle driver the connection string I use is the following

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.oracle',
        'NAME': 'DBARS_PROD',
        'USER': 'userhere',
        'PASSWORD': 'passhere',


        }
}

If I use the sqlite3 that comes by default the project runs without errors.