[ostree] pull: make slightly clearer when failing for missing xattrs support

[Giuseppe Scrivano <gscrivano src gnome org>]

commit f506644830c269ece5dbf3aaa4874593c4d85b2c
Author: Giuseppe Scrivano <gscrivan redhat com>
Date:   Fri Nov 6 11:47:15 2015 +0100

    pull: make slightly clearer when failing for missing xattrs support
    
    It is not clear why pull fails on tmpfs.  The additional message might
    be helpful.
    
    Signed-off-by: Giuseppe Scrivano <gscrivan redhat com>

 src/libostree/ostree-repo-commit.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/src/libostree/ostree-repo-commit.c b/src/libostree/ostree-repo-commit.c
index a761a8a..7cc3e27 100644
--- a/src/libostree/ostree-repo-commit.c
+++ b/src/libostree/ostree-repo-commit.c
@@ -103,6 +103,7 @@ write_file_metadata_to_xattr (int fd,
   if (G_UNLIKELY (res == -1))
     {
       gs_set_error_from_errno (error, errno);
+      g_prefix_error (error, "Unable to set xattr: ");
       return FALSE;
     }