Djangogirlsのチュートリアルでmodels.py が実行できない

前提・実現したいこと

Djangogirlsというサイトのチュートリアルに従いブログの作成をしていたところ、models.pyの編集したところでエラー出てしまい困っています。お助け頂きたいです。
■ チュートリアル 
https://djangogirlsjapan.gitbooks.io/workshop_tutorialjp/content/how_the_internet_works/index.html

発生している問題・エラーメッセージ

Traceback (most recent call last):
  File "/Users/you/djangogirls5/blog/models.py", line 8, in <module>
    class Post(models.Model):
  File "/Users/you/djangogirls5/blog/models.py", line 9, in Post
    author = models.ForeignKey('auth.User')
  File "/Library/Python/2.7/site-packages/django/db/models/fields/related.py", line 846, in __init__
    to, on_delete, from_fields=['self'], to_fields=[to_field], **kwargs)
  File "/Library/Python/2.7/site-packages/django/db/models/fields/related.py", line 491, in __init__
    super(ForeignObject, self).__init__(rel=rel, **kwargs)
  File "/Library/Python/2.7/site-packages/django/db/models/fields/__init__.py", line 172, in __init__
    self.db_tablespace = db_tablespace or settings.DEFAULT_INDEX_TABLESPACE
  File "/Library/Python/2.7/site-packages/django/conf/__init__.py", line 56, in __getattr__
    self._setup(name)
  File "/Library/Python/2.7/site-packages/django/conf/__init__.py", line 39, in _setup
    % (desc, ENVIRONMENT_VARIABLE))
django.core.exceptions.ImproperlyConfigured: Requested setting DEFAULT_INDEX_TABLESPACE, but settings are not configured. You must either define the environment variable DJANGO_SETTINGS_MODULE or call settings.configure() before accessing settings.
[Finished in 1.809s]
Git
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該当のソースコード

#models.py

#!/usr/bin/python

from django.db import models
from django.utils import timezone

class Post(models.Model):
    author = models.ForeignKey('auth.User')
    title = models.CharField(max_length=200)
    text = models.TextField()
    created_date = models.DateTimeField(
            default=timezone.now)
    published_date = models.DateTimeField(
            blank=True, null=True)

    def publish(self):
        self.published_date = timezone.now()
        self.save()

    def __str__(self):
        return self.title

該当のソースコード

#settings.py

"""
Django settings for mysite project.

Generated by 'django-admin startproject' using Django 1.11.

For more information on this file, see
https://docs.djangoproject.com/en/1.11/topics/settings/

For the full list of settings and their values, see
https://docs.djangoproject.com/en/1.11/ref/settings/
"""

import os

# Build paths inside the project like this: os.path.join(BASE_DIR, ...)
BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))


# Quick-start development settings - unsuitable for production
# See https://docs.djangoproject.com/en/1.11/howto/deployment/checklist/

# SECURITY WARNING: keep the secret key used in production secret!
SECRET_KEY = 'a50vp3o@9#*tldh*3bzb6voehi_)xv#bu&p1+i2ed1cf6!hu4('

# SECURITY WARNING: don't run with debug turned on in production!
DEBUG = True

ALLOWED_HOSTS = []


# Application definition

INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'blog'
]

MIDDLEWARE = [
    'django.middleware.security.SecurityMiddleware',
    'django.contrib.sessions.middleware.SessionMiddleware',
    'django.middleware.common.CommonMiddleware',
    'django.middleware.csrf.CsrfViewMiddleware',
    'django.contrib.auth.middleware.AuthenticationMiddleware',
    'django.contrib.messages.middleware.MessageMiddleware',
    'django.middleware.clickjacking.XFrameOptionsMiddleware',
]

ROOT_URLCONF = 'mysite.urls'

TEMPLATES = [
    {
        'BACKEND': 'django.template.backends.django.DjangoTemplates',
        'DIRS': [],
        'APP_DIRS': True,
        'OPTIONS': {
            'context_processors': [
                'django.template.context_processors.debug',
                'django.template.context_processors.request',
                'django.contrib.auth.context_processors.auth',
                'django.contrib.messages.context_processors.messages',
            ],
        },
    },
]

WSGI_APPLICATION = 'mysite.wsgi.application'


# Database
# https://docs.djangoproject.com/en/1.11/ref/settings/#databases

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
    }
}


# Password validation
# https://docs.djangoproject.com/en/1.11/ref/settings/#auth-password-validators

AUTH_PASSWORD_VALIDATORS = [
    {
        'NAME': 'django.contrib.auth.password_validation.UserAttributeSimilarityValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.MinimumLengthValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.CommonPasswordValidator',
    },
    {
        'NAME': 'django.contrib.auth.password_validation.NumericPasswordValidator',
    },
]


# Internationalization
# https://docs.djangoproject.com/en/1.11/topics/i18n/

LANGUAGE_CODE = 'ja-JP'

TIME_ZONE = 'Asia/Tokyo'

USE_I18N = True

USE_L10N = True

USE_TZ = False


# Static files (CSS, JavaScript, Images)
# https://docs.djangoproject.com/en/1.11/howto/static-files/

STATIC_URL = '/static/'

試したこと

1.   djangoチュートリアルに従い、
   export DJANGO_SETTINGS_MODULE=mysite.settings
   django-admin runserver　を実行したところ、ModuleNotFoundError: No module named 'mysite'というエラーが出ました。

■https://docs.djangoproject.com/ja/1.11/topics/settings/#using-settings-without-setting-django-settings-module

1.   python2,3ともにインストールしているので以下のサイトに従いmodels.pyのシェバン行を#!/usr/bin/python3に変更しましたが、以下のようにエラーが出ました。

■https://blogware.info/python/prog/shebang/

Unable to run

/usr/bin/python3
Did you start Atom from the command line?

  atom .
Is it in your PATH?

PATH: /Library/Frameworks/Python.framework/Versions/3.6/bin:/Library/Frameworks/Python.framework/Versions/3.6/bin:/Library/Frameworks/Python.framework/Versions/3.6/bin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/Library/Frameworks/Python.framework/Versions/3.6/bin

補足情報(言語/FW/ツール等のバージョンなど)

より詳細な情報

python3.6.2
mac OS