[babl] babl-fish-path: add debug print message when no fast paths were found

[Øyvind Kolås <ok src gnome org>]

commit 0c2baa9b15adde7ee11116d505748aefdbb77b66
Author: Øyvind Kolås <pippin gimp org>
Date:   Sat Dec 10 19:41:39 2016 +0100

    babl-fish-path: add debug print message when no fast paths were found
    
    Messages get printed when the environment variable BABL_DEBUG_CONVERSIONS is
    set, which also inhibits loading of babl fish cache.

 babl/babl-fish-path.c |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)
---
diff --git a/babl/babl-fish-path.c b/babl/babl-fish-path.c
index 23e7757..7a71184 100644
--- a/babl/babl-fish-path.c
+++ b/babl/babl-fish-path.c
@@ -341,6 +341,11 @@ babl_fish_path (const Babl *source,
     {
       babl_free (babl);
       babl_mutex_unlock (babl_format_mutex);
+
+      if (debug_conversions)
+        fprintf (stderr, "babl: no fast path for \"%s\" to \"%s\"\n",
+           babl_get_name (source),
+           babl_get_name (destination));
       return NULL;
     }