Specify No such file in error message

Author: gkobeaga

src/cmd/opt.c

@@ -88,7 +88,6 @@ __solver_opt(int argc, char *argv[])
         break;
     }
     default:
-        printf("Unknown problem %d.\n", data->prob);
         return 1;
     }
 

src/data/io/read.c

@@ -502,7 +502,7 @@ data_read(const char *fname, int format)
     file = fopen(fname, "r");
     if (!file)
     {
-        printf("Unable to open '%s'\n", fname);
+        printf("Unable to open '%s': No such file\n", fname);
         goto done;
     }