LSOpenURLsWithRole() failed with error -10810 Can't open 'Install OS X Yosemite.app'
That would seem to imply the executable within the package isn't actually executable. 

Where did you get it from?
If not Apple, I'd leave it well alone. If it was from Apple, try this in Terminal

chmod +x /Applications/Install\ OS\ X\ Yosemite.app/Contents/MacOS/InstallAssistant