When trying to verify the signature of a binary (Windows 7, GpgEX Shell Extension > "Prüfen"), I was confronted with a strange error message (I suspect the "\r" is an attempt to create a line break?):
Fehlermeldung der GnuPG Benutzerschnittstelle:\r Input/output error
It cost my quite some time to find out what caused this error message: The signature's file name was not identical with the file to be verified.
To take the screenshot, I modified a valid signature's file name by replacing an underscore with a minus sign, and you will agree that such a small difference is hard to spot.
While you can argue that this is a synthetic case (because signatures are machine-generated and thus comply with naming rules), it can really happen that a user (me, for exeample...) downloads an x64 binary from a website and accidentally chooses the x86 signature file download for verification.
In this case, the error message is not helpful and even misleading.
I propose you change the error message to be more specific (that is, if you can really distinguish between "file not existent" and "no access rights"?), for example:
Input/output error: 'C:\temp\download.exe' does not exist
Note: when enriching the error message with the expected file name, please take care that the full path is readable within the small message window!