Wrong error caught in RegistryInfo.lookup

[shortenda]

Hello,

I believe that RegistryInfo.lookup should be except'ing WindowsError instead of IOError when it calls open key

I ran into this issue trying to install a package. Sorry if this isn't correct as I'm not familiar with this project.

Thanks,
David

[jaraco]

What's the benefit of catching WindowsError instead of IOError? I see that WindowsError is a subclass of OSError, of which IOError is also a subclass on Python 3 (but apparently not Python 2).

What issue did you encounter? Is it possible there are conditions where a WindowsError might be raised, so perhaps multiple exceptions should be caught?

[shortenda]

OpenKey throws a WindowsError if the registry key it's looking for can't be found in python2. So in python2, where WindowsError is distinct from and not a subclass of IOError, a lookup attempt on a missing registry key is not caught and crashes setuptools. In my case a missing visual studio registry key was stopping the install, whereas the intention was to fall back to a default.

It actually seems like it would be most prudent to catch EnvironmentError, apparently this is what winreg.OpenKey throws in python3 and would also catch WindowsError in python2.

[jaraco]

@JGoutin Would you be willing to review? Do you concur with shortenda's analysis?

[JGoutin]

On Python 3, if OpenKey don't found the key a FileNotFoundError is raised (subclass of IOError, FileNotFoundError is not available on Python 2). But, indeed, like wrote in the doc and said by shortenda, this function may also raise WindowsError (On Python 2) or OSError (On Python 3).

IOError have been merged in OSError only since Python 3.3.

So, to cover all case, we need to except OSError and IOError.