title: The empty path didn't match any of these. (Python3, Django, URLS)
body: <p>I'm learning Python3. I installed python and django on my webserver.
  But I have a problem with URLs. </p>
  
  <p>Here's what I tried :</p>
  
  <ol>
  <li>sctructure:<br /><pre>
  expnk.ru
  HelloDjango (1)
    HelloDjango (2)
       setting.py
       ..........
       urls.py
    cat
    ...
    any apps</pre></li>
  <li>run "cat" from ssh command: <br />
  <code>python3 manage.py startapp cat</code></li>
  <li><p>next im going to HelloDjango (2) file and edited file <code>setting.py</code>, for <code>INSTALLED_APPS</code> and added <code>'cat'</code></p></li>
  <li><p>then I'm doing <code>HelloDjango (2) -&gt; urls.py</code>. I added to this file the next strings: <br /></p></li>
  </ol>
  
  <pre><code>from django.conf.urls import url, include
  from django.contrib import admin
  
  urlpatterns = [
      url(r'^cat/', include('cat.urls')),
      url(r'^admin/', admin.site.urls),
      url(r'^blog/', include('blog.urls')),
      url(r'^test/', include('test.urls')),
  ]
  </code></pre>
  
  <ol start="5">
  <li>then I do: <code>cat -&gt; urls.py</code> and add to this file:</li>
  </ol>
  
  <pre><code>from django.conf.urls import url, include
  from django.contrib import admin
  from . import views
  
  urlpatterns = [
      url(r'^$', views.index, name='index'),
  ]
  
  </code></pre>
  
  <ol start="6">
  <li>lastly, I edited file <code>views</code>, code from this file is below:</li>
  </ol>
  
  <pre><code>from django.shortcuts import render
  from django.http import HttpResponse
  
  def index(response):
      return HttpResponse("Hello world!")
  
  # Create your views here.
  
  </code></pre>
  
  <p>I created the cat application similar to the blog application, as a result: the blog is running, but cat is not.</p>