D5772: hg: raise Abort on invalid path

[Yuya Nishihara]

>   > Currently, some os.path functions when opening repositories may
>   >  raise an uncaught TypeError or ValueError if the path is invalid.
>   
>   What kind of "invalid"? If the path doesn't exist? Or only if the path variable is of the wrong type (not bytes? not unicode? neither?)?

It's NUL byte in path string.