title: Kivy how to use Builder.load_file?
body: <p>I have the following directory structure:</p>
  
  <pre><code>project/
      controller/
          __init__.py
          app1.py
      view/
          app1.kv
      main.py
  </code></pre>
  
  <p>My <code>main.py</code>is:</p>
  
  <pre><code>from controller.app1 import App1
  
  
  def main():
      App1().run()
  
  
  if __name__ == '__main__':
      main()
  </code></pre>
  
  <p>My <code>app1.py</code>is:</p>
  
  <pre><code>from kivy.app import App
  from kivy.lang import Builder
  
  Builder.load_file('view/app1.kv')
  
  class App1(App):
      pass
  </code></pre>
  
  <p>I am running:</p>
  
  <pre><code>kivy main.py
  </code></pre>
  
  <p>However, the contents of my Kivy is not loaded.</p>