Diagnosing Mac apps which won’t open (error -10810)

Occasionally, my mac applications end up in a corrupt state where they won’t open. I recently encountered this with Deluge. The first step to diagnose is to open Terminal and open them in the terminal via

$ open -a deluge  # This name is same as the name of the app (minus the ".app" portion).
LSOpenURLsWithRole() failed for the application /usr/local/Caskroom/deluge/1.3.12/Deluge.app with error -10810.

Now, the error is more diagnosable but still cryptic. Deluge.app above is a directory and we can navigate to the binary located at Deluge.app/Contents/MacOS/Deluge and execute the actual binary to see a more actionable error

$ /usr/local/Caskroom/deluge/1.3.12/Deluge.app/Contents/MacOS/Deluge
Traceback (most recent call last):
  File "/usr/local/Caskroom/deluge/1.3.12/Deluge.app/Contents/MacOS/Deluge-bin", line 5, in <module>
    from pkg_resources import load_entry_point
  File "pkg_resources/__init__.pyc", line 37, in <module>
  File "email/parser.pyc", line 12, in <module>
  File "email/feedparser.pyc", line 27, in <module>
  File "email/message.pyc", line 16, in <module>
  File "email/charset.pyc", line 13, in <module>
  File "email/base64mime.pyc", line 40, in <module>
  File "email/utils.pyc", line 29, in <module>
  File "urllib.pyc", line 1414, in <module>

ImportError: dlopen(/usr/local/Caskroom/deluge/1.3.12/Deluge.app/Contents/Resources/lib/python/lib-dynload/_scproxy.so, 2): Symbol not found: _inflateValidate
  Referenced from: /System/Library/Frameworks/ImageIO.framework/Versions/A/Resources/libPng.dylib
  Expected in: /usr/local/Caskroom/deluge/1.3.12/Deluge.app/Contents/Resources/lib/libz.1.dylib
 in /System/Library/Frameworks/ImageIO.framework/Versions/A/Resources/libPng.dylib

Now, this is something meaningful and Google search worthy. Googling for “Symbol not found: _inflateValidate” takes us to the most likely cause. In my case, uninstall followed by the reinstall of Deluge fixed it.