Why isn't my webapp2 import / Google App Engine "Hello, World" working?
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While I'm able to get my "Hello, World" program running on Google App Engine (GAE), it only works when I create a version that doesn't rely on the webapp2 import. Does anyone know why the import isn't working and what I need to do to fix it?

Details below.

Thanks in advance for any suggestions!

Version of helloworld.py that works:

    print 'Content-Type: text/plain'
    print ''
    print 'Hello, World!!'

Version of helloworld.py that does not work:

    import webapp2
    
    class MainPage(webapp2.RequestHandler):
        def get(self):
            self.response.headers['Content-Type'] = 'text/plain'
            self.response.out.write('Hello, World!')
    
    app = webapp2.WSGIApplication([('/', MainPage)], debug=True)

This second version renders as a blank page.

I think the problem is that the webapp2 import isn't working. When I run python from within the same directory as my hello world program from the command line I get the following:

    Brians-MacBook-Air-2:app_engine_hello_world brian$ python
    Python 2.7.2 (v2.7.2:8527427914a2, Jun 11 2011, 15:22:34) 
    [GCC 4.2.1 (Apple Inc. build 5666) (dot 3)] on darwin
    Type "help", "copyright", "credits" or "license" for more information.
    >>> import webapp2
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    ImportError: No module named webapp2

However, I see webapp2.py in the following directory:

    Brians-MacBook-Air-2:webapp2 brian$ pwd
    /Users/brian/Repos/app_engine_hello_world/build/webapp2

Also, I'm running python 2.7 installed in the following location:

    Brians-MacBook-Air-2:app_engine_hello_world brian$ which python
    /Library/Frameworks/Python.framework/Versions/2.7/bin/python