mark all "Hash Sum mismatch" strings as translateable

apt-pkg/acquire-item.cc

@@ -1710,7 +1710,7 @@ void pkgAcqFile::Done(string Message,unsigned long Size,string CalcHash,
    if(!ExpectedHash.empty() && ExpectedHash.toStr() != CalcHash)
    {
       Status = StatError;
-      ErrorText = "Hash Sum mismatch";
+      ErrorText = _("Hash Sum mismatch");
       Rename(DestFile,DestFile + ".FAILED");
       return;
    }