old_contents: """A backend for the Elasticsearch search engine."""
  
  from __future__ import unicode_literals
  
  from django import forms
  from django.core.exceptions import ValidationError
  from django.utils.translation import ugettext, ugettext_lazy as _
  
  from reviewboard.search.search_backends.base import (SearchBackend,
                                                       SearchBackendForm)
  
  
  class ElasticsearchConfigForm(SearchBackendForm):
      """A form for configuring the Elasticsearch search backend."""
  
      url = forms.URLField(
          label=_('Elasticsearch URL'),
          help_text=_('The URL of the Elasticsearch server.'),
          widget=forms.TextInput(attrs={'size': 80}))
  
      index_name = forms.CharField(
          label=_('Elasticsearch index name'),
          help_text=_('The name of the Elasticsearch index.'),
          widget=forms.TextInput(attrs={'size': 40}))
  
  
  class ElasticsearchBackend(SearchBackend):
      """A search backend for integrating with Elasticsearch"""
  
      search_backend_id = 'elasticsearch'
      name = _('Elasticsearch')
      haystack_backend_name = ('haystack.backends.elasticsearch_backend.'
                               'ElasticsearchSearchEngine')
      default_settings = {
          'URL': 'http://127.0.0.1:9200/',
          'INDEX_NAME': 'reviewboard',
      }
      config_form_class = ElasticsearchConfigForm
      form_field_map = {
          'url': 'URL',
          'index_name': 'INDEX_NAME',
      }
  
      def validate(self):
          """Ensure that the elasticsearch Python module is installed.
  
          Raises:
              django.core.exceptions.ValidationError:
                  Raised if the ``elasticsearch`` module is not installed.
          """
          try:
              import elasticsearch  # noqa
          except ImportError:
              raise ValidationError(ugettext(
                  'The "elasticsearch" module is required to use the '
                  'Elasticsearch search engine.'
              ))
  
new_contents: """A backend for the Elasticsearch search engine."""
  
  from __future__ import unicode_literals
  
  from importlib import import_module
  
  from django import forms
  from django.core.exceptions import ValidationError
  from django.utils.translation import ugettext, ugettext_lazy as _
  
  from reviewboard.search.search_backends.base import (SearchBackend,
                                                       SearchBackendForm)
  
  
  class ElasticsearchConfigForm(SearchBackendForm):
      """A form for configuring the Elasticsearch search backend."""
  
      url = forms.URLField(
          label=_('Elasticsearch URL'),
          help_text=_('The URL of the Elasticsearch server.'),
          widget=forms.TextInput(attrs={'size': 80}))
  
      index_name = forms.CharField(
          label=_('Elasticsearch index name'),
          help_text=_('The name of the Elasticsearch index.'),
          widget=forms.TextInput(attrs={'size': 40}))
  
  
  class ElasticsearchBackend(SearchBackend):
      """A search backend for integrating with Elasticsearch"""
  
      search_backend_id = 'elasticsearch'
      name = _('Elasticsearch')
      haystack_backend_name = ('haystack.backends.elasticsearch_backend.'
                               'ElasticsearchSearchEngine')
      default_settings = {
          'URL': 'http://127.0.0.1:9200/',
          'INDEX_NAME': 'reviewboard',
      }
      config_form_class = ElasticsearchConfigForm
      form_field_map = {
          'url': 'URL',
          'index_name': 'INDEX_NAME',
      }
  
      def validate(self):
          """Ensure that the elasticsearch Python module is installed.
  
          Raises:
              django.core.exceptions.ValidationError:
                  Raised if the ``elasticsearch`` module is not installed.
          """
          try:
              import_module('elasticsearch')
          except ImportError:
              raise ValidationError(ugettext(
                  'The "elasticsearch" module is required to use the '
                  'Elasticsearch search engine.'
              ))
  
subject: Use importlib to check for elasticsearch instead of import statement