title: UnicodeEncodeError raised when 'createsuperuser' is called
body: <p>I am trying to deploy my Django application (2.1.5 with Python 3.6.6) on my server with a PostGreSQL database.
  I did a 'makemigrations' and 'migrate' as usual and then I can't create a super user with the command 'createsuperuser':</p>
  
  <pre><code>[alex@web574 myproject]$ python3.6 manage.py createsuperuser
  Nom d'utilisateur (leave blank to use 'alex'): 
  Traceback (most recent call last):
    File "manage.py", line 15, in &lt;module&gt;
      execute_from_command_line(sys.argv)
    File "/home/alex/webapps/global_hse_project/lib/python3.6/Django-2.1.5-py3.6.egg/django/core/management/__init__.py", line 381, in execute_from_command_line
      utility.execute()
    File "/home/alex/webapps/global_hse_project/lib/python3.6/Django-2.1.5-py3.6.egg/django/core/management/__init__.py", line 375, in execute
      self.fetch_command(subcommand).run_from_argv(self.argv)
    File "/home/alex/webapps/global_hse_project/lib/python3.6/Django-2.1.5-py3.6.egg/django/core/management/base.py", line 316, in run_from_argv
      self.execute(*args, **cmd_options)
    File "/home/alex/webapps/global_hse_project/lib/python3.6/Django-2.1.5-py3.6.egg/django/contrib/auth/management/commands/createsuperuser.py", line 60, in execute
      return super().execute(*args, **options)
    File "/home/alex/webapps/global_hse_project/lib/python3.6/Django-2.1.5-py3.6.egg/django/core/management/base.py", line 353, in execute
      output = self.handle(*args, **options)
    File "/home/alex/webapps/global_hse_project/lib/python3.6/Django-2.1.5-py3.6.egg/django/contrib/auth/management/commands/createsuperuser.py", line 139, in handle
      input_value = self.get_input_data(field, message)
    File "/home/alex/webapps/global_hse_project/lib/python3.6/Django-2.1.5-py3.6.egg/django/contrib/auth/management/commands/createsuperuser.py", line 194, in get_input_data
      raw_value = input(message)
  UnicodeEncodeError: 'ascii' codec can't encode character '\xe9' in position 8: ordinal not in range(128)
  </code></pre>
  
  <p>I found on Google to add:</p>
  
  <pre><code># -*- Coding: utf-8 -*-
  </code></pre>
  
  <p>at the top of the file but it doesn't work, same result with the variable DEFAULT_CHARSET (<a href="https://docs.djangoproject.com/en/dev/ref/settings/#std:setting-DEFAULT_CHARSET" rel="nofollow noreferrer">https://docs.djangoproject.com/en/dev/ref/settings/#std:setting-DEFAULT_CHARSET</a>).
  My PostGreSQL database are asking for utf-8 encoding.</p>