py2app .app crashes... but only when downloaded (quarantine)

I've got a bizarre issue here. I've built a .app with py2app 0.10 on my OS
X 10.9.5 machine using python.org Python 2.7.12. It's a Tkinter
application, with a relatively simple `setup.py`. The .app works
beautifully when I build it and double-click it locally, and when I
"sneaker net" it to a 10.10.5 non-development Mac.

However, if I *download* the exact same file from the Internet, Apple's
Gatekeeper says that this "is an application downloaded from the Internet.
Are you sure you want to open it?" When I click "Open", my Tkinter GUI very
briefly appears, and then CRASH.

When I double-click the downloaded version a second time (after its first
crash), it seem to work fine. Presumably OS X is clearing the
com.apple.quarantine attribute during the failed first run?

Does anyone have a clue as to what could be causing this quarantine-related
crash?!

The crash diagnostics follow.

You may download my .app file from the following URL if you'd like to try
it yourself:


http://myotisoft.com/wp-content/uploads/2016/10/Myotisoft_Transect-1.1.4-MacOSX.zip

Thanks for any help you can offer!

- DR


-- 
David A. Riggs <[email protected]>

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