title: Django issue with argon2 hasher in live production
body: <p>So I have just setup my Digital Ocean droplet (server) and have been working to get this site to work, however I have been coming across error after error. I finally got the site to load the login page (which is what should happen), but when I login I get an error that Argon2 Pass Hasher couldn't load. I really have no idea what the problem is, as everything was working perfectly while in development.</p>
  
  <p>Here is the error:</p>
  
  <pre><code>ValueError at /accounts/login/
  Couldn't load 'Argon2PasswordHasher' algorithm library: No module named argon2
  </code></pre>
  
  <p>Here are my settings:</p>
  
  <pre><code>"""
  Django settings for django_project project.
  
  Generated by 'django-admin startproject' using Django 1.8.7.
  
  For more information on this file, see
  https://docs.djangoproject.com/en/1.8/topics/settings/
  
  For the full list of settings and their values, see
  https://docs.djangoproject.com/en/1.8/ref/settings/
  """
  
  # Build paths inside the project like this: os.path.join(BASE_DIR, ...)
  import os
  
  BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
  TEMPLATE_DIR = os.path.join(BASE_DIR, 'templates')
  MEDIA_DIR = os.path.join(BASE_DIR, 'media')
  
  
  # 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 = 'h&amp;*(yq942_a^pa+ty&amp;wh(bl9s4d#z^*_6cmeb#5&amp;49jb^r$&amp;!f'
  
  # 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',
      'django.contrib.sites',
  
      'users',
      'feed',
      'blog',
  
      'allauth',
      'allauth.account',
      'allauth.socialaccount',
  )
  
  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 = 'django_project.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 = 'django_project.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'),
      }
  }
  
  # Password validation
  # https://docs.djangoproject.com/en/1.11/ref/settings/#auth-password-validators
  
  PASSWORD_HASHERS = [
      'django.contrib.auth.hashers.Argon2PasswordHasher',
      'django.contrib.auth.hashers.BCryptSHA256PasswordHasher',
      'django.contrib.auth.hashers.BCryptPasswordHasher',
      'django.contrib.auth.hashers.PBKDF2PasswordHasher',
      'django.contrib.auth.hashers.PBKDF2SHA1PasswordHasher',
  ]
  
  
  # Internationalization
  # https://docs.djangoproject.com/en/1.8/topics/i18n/
  
  LANGUAGE_CODE = 'en-us'
  
  TIME_ZONE = 'UTC'
  
  USE_I18N = True
  
  USE_L10N = True
  
  USE_TZ = True
  
  SITE_ID = 1
  
  
  # Static files (CSS, JavaScript, Images)
  # https://docs.djangoproject.com/en/1.8/howto/static-files/
  
  STATIC_URL = '/static/'
  STATIC_ROOT = '/static/'
  STATIC_DIR = os.path.join(BASE_DIR,'static')
  
  STATICFILES_DIRS = [
      STATIC_DIR,
  ]
  
  
  #MEDIA
  MEDIA_ROOT = MEDIA_DIR
  MEDIA_URL = '/media/'
  
  
  LOGIN_URL = '/user_login'
  
  # settings
  ACCOUNT_AUTHENTICATION_METHOD = 'username_email'
  
  ACCOUNT_USERNAME_REQUIRED = True
  ACCOUNT_UNIQUE_USERNAME =True
  ACCOUNT_SIGNUP_EMAIL_ENTER_TWICE =False
  ACCOUNT_SIGNUP_PASSWORD_ENTER_TWICE =True
  ACCOUNT_EMAIL_CONFIRMATION_EXPIRE_DAYS =3
  ACCOUNT_LOGIN_ATTEMPTS_LIMIT = 5
  ACCOUNT_LOGOUT_ON_PASSWORD_CHANGE =True
  ACCOUNT_SESSION_REMEMBER =None
  ACCOUNT_ADAPTER ='allauth.account.adapter.DefaultAccountAdapter'
  
  ACCOUNT_UNIQUE_EMAIL =True
  # SOCIALACCOUNT_AUTO_SIGNUP =True
  
  # SOCIALACCOUNT_EMAIL_REQUIRED ='ACCOUNT_EMAIL_REQUIRED'
  # SOCIALACCOUNT_QUERY_EMAIL ='ACCOUNT_EMAIL_REQUIRED'
  
  
  ACCOUNT_EMAIL_REQUIRED = True
  ACCOUNT_EMAIL_CONFIRMATION_HMAC =True
  ACCOUNT_EMAIL_VERIFICATION = 'none'
  #ACCOUNT_EMAIL_VERIFICATION = 'optional'
  #ACCOUNT_EMAIL_VERIFICATION = 'mandatory'
  
  
  EMAIL_BACKEND = 'django.core.mail.backends.smtp.EmailBackend'
  EMAIL_HOST = 'smtp.sendgrid.com'
  EMAIL_HOST_PASSWORD = 'password'
  EMAIL_HOST_USER = 'username'
  EMAIL_PORT = 587
  EMAIL_USE_TLS = True
  DEFAULT_FROM_EMAIL = 'support@yoursite.com'
  
  
  
  # Build paths inside the project like this: os.path.join(BASE_DIR, ...)
  # Allow Django from all hosts. This snippet is installed from
  # /var/lib/digitalocean/allow_hosts.py
  
  import os
  import netifaces
  
  # Find out what the IP addresses are at run time
  # This is necessary because otherwise Gunicorn will reject the connections
  def ip_addresses():
      ip_list = []
      for interface in netifaces.interfaces():
          addrs = netifaces.ifaddresses(interface)
          for x in (netifaces.AF_INET, netifaces.AF_INET6):
              if x in addrs:
                  ip_list.append(addrs[x][0]['addr'])
      return ip_list
  
  # Discover our IP address
  ALLOWED_HOSTS = ip_addresses()
  </code></pre>
  
  <p>Here is the traceback:</p>
  
  <pre><code>Traceback Switch to copy-and-paste view
  
  /usr/local/lib/python2.7/dist-packages/django/core/handlers/exception.py in inner
              response = get_response(request) ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py in _legacy_get_response
              response = self._get_response(request) ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py in _get_response
                  response = self.process_exception_by_middleware(e, request) ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/core/handlers/base.py in _get_response
                  response = wrapped_callback(request, *callback_args, **callback_kwargs) ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/views/generic/base.py in view
              return self.dispatch(request, *args, **kwargs) ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/utils/decorators.py in _wrapper
              return bound_func(*args, **kwargs) ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/views/decorators/debug.py in sensitive_post_parameters_wrapper
              return view(request, *args, **kwargs) ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/utils/decorators.py in bound_func
                  return func.__get__(self, type(self))(*args2, **kwargs2) ...
  ▶ Local vars
  /home/django/django_project/allauth/account/views.py in dispatch
          return super(LoginView, self).dispatch(request, *args, **kwargs) ...
  ▶ Local vars
  /home/django/django_project/allauth/account/views.py in dispatch
                                              **kwargs) ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/views/generic/base.py in dispatch
          return handler(request, *args, **kwargs) ...
  ▶ Local vars
  /home/django/django_project/allauth/account/views.py in post
          if form.is_valid(): ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/forms/forms.py in is_valid
          return self.is_bound and not self.errors ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/forms/forms.py in errors
              self.full_clean() ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/forms/forms.py in full_clean
          self._clean_form() ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/forms/forms.py in _clean_form
              cleaned_data = self.clean() ...
  ▶ Local vars
  /home/django/django_project/allauth/account/forms.py in clean
              **credentials) ...
  ▶ Local vars
  /home/django/django_project/allauth/account/adapter.py in authenticate
          user = authenticate(request=request, **credentials) ...
  ▶ Local vars
  /home/django/django_project/allauth/compat.py in authenticate
          return authenticate(request=request, **credentials) ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/contrib/auth/__init__.py in authenticate
              user = _authenticate_with_backend(backend, backend_path, request, credentials) ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/contrib/auth/__init__.py in _authenticate_with_backend
      return backend.authenticate(*args, **credentials) ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/contrib/auth/backends.py in authenticate
              if user.check_password(password) and self.user_can_authenticate(user): ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/contrib/auth/base_user.py in check_password
          return check_password(raw_password, self.password, setter) ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/contrib/auth/hashers.py in check_password
      must_update = hasher_changed or preferred.must_update(encoded) ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/contrib/auth/hashers.py in must_update
          argon2 = self._load_library() ...
  ▶ Local vars
  /usr/local/lib/python2.7/dist-packages/django/contrib/auth/hashers.py in _load_library
                                   (self.__class__.__name__, e)) ...
  ▶ Local vars
  </code></pre>
  
  <p>Please help, this issue seems to be rather specific so I haven't been able to find very much on it...</p>