Debugging - Show error on page or terminal or log

[joseluizcoe]

When i'm doing something wrong, grow.io show me one blank page and don't give me any information about the error. How can i debug to know what am i doing wrong?

This console message don't tell me where is the error in my code:

WSGI application error
Traceback (most recent call last):
File "/Users/joseluizcoe/myapp/lib/python2.7/site-packages/twisted/python/threadpool.py", line 262, in
inContext.theWork = lambda: context.call(ctx, func, _args, *_kw)
File "/Users/joseluizcoe/myapp/lib/python2.7/site-packages/twisted/python/context.py", line 118, in callWithContext
return self.currentContext().callWithContext(ctx, func, _args, *_kw)
File "/Users/joseluizcoe/myapp/lib/python2.7/site-packages/twisted/python/context.py", line 83, in callWithContext
self.contexts.pop()
File "/Users/joseluizcoe/myapp/lib/python2.7/site-packages/twisted/web/wsgi.py", line 521, in run
self.started = True
--- ---
File "/Users/joseluizcoe/myapp/lib/python2.7/site-packages/twisted/web/wsgi.py", line 496, in run
appIterator = self.application(self.environ, self.startResponse)
File "/Users/joseluizcoe/myapp/lib/python2.7/site-packages/werkzeug/wsgi.py", line 579, in call
return self.app(environ, start_response)
File "/Users/joseluizcoe/myapp/lib/python2.7/site-packages/grow/server/main.py", line 97, in call
return self.wsgi_app(environ, start_response)
File "/Users/joseluizcoe/myapp/lib/python2.7/site-packages/grow/server/main.py", line 93, in wsgi_app
response = self.dispatch_request(request)
File "/Users/joseluizcoe/myapp/lib/python2.7/site-packages/grow/server/main.py", line 89, in dispatch_request
return self.handle_exception(request, e)
File "/Users/joseluizcoe/myapp/lib/python2.7/site-packages/grow/server/main.py", line 101, in handle_exception
if isinstance(exc, webob.exc.HTTPException):
exceptions.AttributeError: 'module' object has no attribute 'exc'

How can i debug my code?