title: error TemplateNotFound: hello.html from flask
body: <pre><code>  File "/usr/local/lib/python2.7/dist-packages/flask/templating.py", line 64, in get_source
      raise TemplateNotFound(template)
  TemplateNotFound: hello.html
  </code></pre>
  
  <p>script of app.py:</p>
  
  <pre><code>from flask import Flask
  from flask import request
  from flask import render_template
  
  APP = Flask(_name__)
  
  @APP.route('/')
  def hello():
        return render_template('hello.html')
  
  if _name__ == '_main__':
      APP.debug=True
      APP.run()
  </code></pre>
  
  <p>My directory structure:</p>
  
  <pre><code>app/
  ├── app.py
  ├── app.py~
  ├── static  
  │   └── style.css
  └── template
        ├── hello.html
        └── hello.html~
  </code></pre>