errors in directory c:\src\blah
c:\src\blah\mumbletool : error error: ???????????????
I guess the tool doesn't know what went wrong either.
Maybe the error message could have been
errors in directory c:\src\blah
c:\src\blah\mumbletool : error error: ¯\_()_/¯
)_/¯
On the other hand, that could very well have been the error message it wanted to print, except that the characters didn't survive the translation to the OEM code page.