version checking needs better error messages

[nachog00]

If the download of binaries falls short, binaries become un-executable.
Version checking doesn't take this into account and outputs "wrong version string" when the version isn't even known.

[ala-mode]

Checking the version string is part of our (maybe over-elaborate) way of verifying that the downloaded files are correct and complete, so this is expected behavior.

That is to say, an incomplete file is not any version of the binary, and thus should fail this check.

[nachog00]

I agree, but the error showed has to change. If the binary isn't executable, we shouldn't be saying "Error: version mismatch".

stdout gives a very explicit message in those cases