title: Django runserver error: unsupported operand type(s) for +=: 'NoneType' and 'str'
body: <p>I'm running a local dev project made with Django. But I cannot have the dev server to start:</p>
  
  <pre><code>(Gaia_database_env)FakeComputer:gaia_database_proj FakeUser$ python manage.py runserver
  Traceback (most recent call last):
    File "manage.py", line 10, in &lt;module&gt;
      execute_from_command_line(sys.argv)
    File "/Users/FakeUser/GoogleDrive/Sites/Gaia_database_env/lib/python3.4/site-packages/django/core/management/__init__.py", line 338, in execute_from_command_line
      utility.execute()
    File "/Users/FakeUser/GoogleDrive/Sites/Gaia_database_env/lib/python3.4/site-packages/django/core/management/__init__.py", line 312, in execute
      django.setup()
    File "/Users/FakeUser/GoogleDrive/Sites/Gaia_database_env/lib/python3.4/site-packages/django/__init__.py", line 18, in setup
      apps.populate(settings.INSTALLED_APPS)
    File "/Users/FakeUser/GoogleDrive/Sites/Gaia_database_env/lib/python3.4/site-packages/django/apps/registry.py", line 108, in populate
      app_config.import_models(all_models)
    File "/Users/FakeUser/GoogleDrive/Sites/Gaia_database_env/lib/python3.4/site-packages/django/apps/config.py", line 198, in import_models
      self.models_module = import_module(models_module_name)
    File "/Users/FakeUser/GoogleDrive/Sites/Gaia_database_env/lib/python3.4/importlib/__init__.py", line 109, in import_module
      return _bootstrap._gcd_import(name[level:], package, level)
    File "&lt;frozen importlib._bootstrap&gt;", line 2254, in _gcd_import
    File "&lt;frozen importlib._bootstrap&gt;", line 2237, in _find_and_load
    File "&lt;frozen importlib._bootstrap&gt;", line 2226, in _find_and_load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 1200, in _load_unlocked
    File "&lt;frozen importlib._bootstrap&gt;", line 1129, in _exec
    File "&lt;frozen importlib._bootstrap&gt;", line 1471, in exec_module
    File "&lt;frozen importlib._bootstrap&gt;", line 321, in _call_with_frames_removed
    File "/Users/FakeUser/GoogleDrive/Sites/Gaia_database_env/lib/python3.4/site-packages/tinymce/models.py", line 6, in &lt;module&gt;
      from tinymce import widgets as tinymce_widgets
    File "/Users/FakeUser/GoogleDrive/Sites/Gaia_database_env/lib/python3.4/site-packages/tinymce/widgets.py", line 10, in &lt;module&gt;
      import tinymce.settings
    File "/Users/FakeUser/GoogleDrive/Sites/Gaia_database_env/lib/python3.4/site-packages/tinymce/settings.py", line 16, in &lt;module&gt;
      JS_ROOT = getattr(settings, 'TINYMCE_JS_ROOT',os.path.join(settings.STATIC_ROOT, 'tiny_mce'))
    File "/Users/FakeUser/GoogleDrive/Sites/Gaia_database_env/bin/../lib/python3.4/posixpath.py", line 82, in join
      path += b
  TypeError: unsupported operand type(s) for +=: 'NoneType' and 'str
  </code></pre>
  
  <p>I'm working into a virtual env with this packages:</p>
  
  <pre><code>(Gaia_database_env)FakeComputer:gaia_database_proj FakeUser$ pip freeze
  Django==1.8.2
  django-bootstrap3==6.1.0
  django-tinymce==1.5.3
  wheel==0.24.0
  </code></pre>
  
  <p>And that's my settings.py:</p>
  
  <pre><code>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/1.8/howto/deployment/checklist/
  
  # SECURITY WARNING: keep the secret key used in production secret!
  SECRET_KEY = 'm6eu#pf_u$upk2qkizhp%gvc6wb%1(alhey8!hqkdzq%j%b4&amp;('
  
  # 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',
      'tinymce',
      'bootstrap3',
      'gaia_app'
  )
  
  MIDDLEWARE_CLASSES = (
      'django.contrib.sessions.middleware.SessionMiddleware',
      'django.middleware.common.CommonMiddleware',
      'django.middleware.csrf.CsrfViewMiddleware',
      'django.contrib.auth.middleware.AuthenticationMiddleware',
      'django.contrib.auth.middleware.SessionAuthenticationMiddleware',
      'django.contrib.messages.middleware.MessageMiddleware',
      'django.middleware.clickjacking.XFrameOptionsMiddleware',
      'django.middleware.security.SecurityMiddleware',
  )
  
  ROOT_URLCONF = 'gaia_database.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 = 'gaia_database.wsgi.application'
  
  
  # Database
  # https://docs.djangoproject.com/en/1.8/ref/settings/#databases
  
  DATABASES = {
      'default': {
          'ENGINE': 'django.db.backends.sqlite3',
          'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
      }
  }
  
  
  # Internationalization
  # https://docs.djangoproject.com/en/1.8/topics/i18n/
  
  LANGUAGE_CODE = 'en-us'
  
  TIME_ZONE = 'CET'
  
  USE_I18N = True
  
  USE_L10N = True
  
  USE_TZ = True
  
  
  # Static files (CSS, JavaScript, Images)
  # https://docs.djangoproject.com/en/1.8/howto/static-files/
  
  STATIC_URL = '/static/'
  </code></pre>
  
  <p>Any idea??</p>
  
  <p>Thanks</p>