vhdx: Fix "log that needs to be replayed" error message

The arguments of error_setg_errno() should yield a short error string
without newlines.

Here, we try to append additional help to the error message by
embedding newlines in the error string.  That's nice, but it's doesn't
play nicely with the errno part.  tests/qemu-iotests/070.out shows the
resulting mess:

    can't open device TEST_DIR/iotest-dirtylog-10G-4M.vhdx: VHDX image file 'TEST_DIR/iotest-dirtylog-10G-4M.vhdx' opened read-only, but contains a log that needs to be replayed.  To replay the log, execute:
     qemu-img check -r all 'TEST_DIR/iotest-dirtylog-10G-4M.vhdx': Operation not permitted

Switch to error_setg() and error_append_hint().  Result:

    can't open device TEST_DIR/iotest-dirtylog-10G-4M.vhdx: VHDX image file 'TEST_DIR/iotest-dirtylog-10G-4M.vhdx' opened read-only, but contains a log that needs to be replayed
    To replay the log, run:
    qemu-img check -r all 'TEST_DIR/iotest-dirtylog-10G-4M.vhdx'
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>
Message-Id: <1450452927-8346-21-git-send-email-armbru@redhat.com>

block/vhdx-log.c

@@ -784,12 +784,13 @@ int vhdx_parse_log(BlockDriverState *bs, BDRVVHDXState *s, bool *flushed,
     if (logs.valid) {
         if (bs->read_only) {
             ret = -EPERM;
-            error_setg_errno(errp, EPERM,
-                             "VHDX image file '%s' opened read-only, but "
-                             "contains a log that needs to be replayed.  To "
-                             "replay the log, execute:\n qemu-img check -r "
-                             "all '%s'",
-                             bs->filename, bs->filename);
+            error_setg(errp,
+                       "VHDX image file '%s' opened read-only, but "
+                       "contains a log that needs to be replayed",
+                       bs->filename);
+            error_append_hint(errp,  "To replay the log, run:\n"
+                              "qemu-img check -r all '%s'\n",
+                              bs->filename);
             goto exit;
         }
         /* now flush the log */

tests/qemu-iotests/070.out

 QA output created by 070
 
 === Verify open image read-only fails, due to dirty log ===
-can't open device TEST_DIR/iotest-dirtylog-10G-4M.vhdx: VHDX image file 'TEST_DIR/iotest-dirtylog-10G-4M.vhdx' opened read-only, but contains a log that needs to be replayed.  To replay the log, execute:
- qemu-img check -r all 'TEST_DIR/iotest-dirtylog-10G-4M.vhdx': Operation not permitted
+can't open device TEST_DIR/iotest-dirtylog-10G-4M.vhdx: VHDX image file 'TEST_DIR/iotest-dirtylog-10G-4M.vhdx' opened read-only, but contains a log that needs to be replayed
+To replay the log, run:
+qemu-img check -r all 'TEST_DIR/iotest-dirtylog-10G-4M.vhdx'
  no file open, try 'help open'
 === Verify open image replays log  ===
 read 18874368/18874368 bytes at offset 0