scripts/get_maintainer.pl: Print proper error message for missing $file

scripts/get_maintainer.pl: Print proper error message for missing $file

If you pass scripts/get_maintainer.pl the name of a FIFO or other
exciting object (/dev/stdin, for example), it would falsely print
"file not found".  Instead: stat the object rather than using -f so
that we do not mind if the object is not a file; and print the errno
value in the error message.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Thomas Huth <thuth@redhat.com>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Stefano Stabellini <sstabellini@kernel.org>
CC: Anthony PERARD <anthony.perard@citrix.com>
Message-Id: <1520535787-6223-13-git-send-email-ian.jackson@eu.citrix.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Ian Jackson <ian.jackson@eu.citrix.com>