diff -r c4bcba8023a9 -r df914f383f5c librazor/transaction.c
--- a/librazor/transaction.c	Sat Aug 23 16:28:31 2014 +0100
+++ b/librazor/transaction.c	Thu Oct 09 17:27:41 2014 +0100
@@ -1,7 +1,7 @@
 /*
  * Copyright (C) 2008  Kristian Høgsberg <krh@redhat.com>
  * Copyright (C) 2008  Red Hat, Inc
- * Copyright (C) 2009, 2011, 2012  J. Ali Harlow <ali@juiblex.co.uk>
+ * Copyright (C) 2009, 2011, 2012, 2014  J. Ali Harlow <ali@juiblex.co.uk>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -778,40 +778,40 @@
 }
 
 static void
-describe_unsatisfied(struct razor_set *set, struct razor_property *rp)
+describe_unsatisfied(struct razor_set *set, struct razor_property *rp,
+		     razor_unsatisfied_callback_t callback, void *data)
 {
 	struct razor_package_iterator pi;
 	struct razor_package *pkg;
 	const char *name, *version, *arch, *pool;
+	const char *requirement;
+	char *s = NULL;
 
 	pool = set->string_pool.data;
-	if (pool[rp->version] == '\0') {
-		razor_package_iterator_init_for_property(&pi, set, rp);
-		while (razor_package_iterator_next(&pi, &pkg,
-						   RAZOR_DETAIL_NAME, &name,
-						   RAZOR_DETAIL_VERSION, &version,
-						   RAZOR_DETAIL_ARCH, &arch,
-						   RAZOR_DETAIL_LAST))
-			fprintf(stderr, "%s is needed by %s-%s.%s\n",
-				&pool[rp->name],
-				name, version, arch);
-	} else {
-		razor_package_iterator_init_for_property(&pi, set, rp);
-		while (razor_package_iterator_next(&pi, &pkg,
-						   RAZOR_DETAIL_NAME, &name,
-						   RAZOR_DETAIL_VERSION, &version,
-						   RAZOR_DETAIL_ARCH, &arch,
-						   RAZOR_DETAIL_LAST))
-			fprintf(stderr, "%s %s %s is needed by %s-%s.%s\n",
-				&pool[rp->name],
-				razor_property_relation_to_string(rp),
-				&pool[rp->version],
-				name, version, arch);
+	if (pool[rp->version] == '\0')
+		requirement = &pool[rp->name];
+	else {
+		s = razor_concat(&pool[rp->name], " ",
+				 razor_property_relation_to_string(rp), " ",
+				 &pool[rp->version], NULL);
+		requirement = s;
 	}
+
+	razor_package_iterator_init_for_property(&pi, set, rp);
+	while (razor_package_iterator_next(&pi, &pkg,
+					   RAZOR_DETAIL_NAME, &name,
+					   RAZOR_DETAIL_VERSION, &version,
+					   RAZOR_DETAIL_ARCH, &arch,
+					   RAZOR_DETAIL_LAST))
+		callback(requirement, pkg, name, version, arch, data);
+
+	if (s)
+		free(s);
 }
 
 RAZOR_EXPORT int
-razor_transaction_describe(struct razor_transaction *trans)
+razor_transaction_unsatisfied(struct razor_transaction *trans,
+			      razor_unsatisfied_callback_t callback, void *data)
 {
 	struct prop_iter rpi;
 	struct razor_property *rp;
@@ -825,7 +825,9 @@
 	prop_iter_init(&rpi, &trans->system);
 	while (prop_iter_next(&rpi, RAZOR_PROPERTY_REQUIRES, &rp)) {
 		if (!(rpi.present[rp - rpi.start] & TRANS_PROPERTY_SATISFIED)) {
-			describe_unsatisfied(trans->system.set, rp);
+			if (callback)
+				describe_unsatisfied(trans->system.set, rp,
+						     callback, data);
 		        unsatisfied++;
 		}
 	}
@@ -833,7 +835,9 @@
 	prop_iter_init(&rpi, &trans->upstream);
 	while (prop_iter_next(&rpi, RAZOR_PROPERTY_REQUIRES, &rp)) {
 		if (!(rpi.present[rp - rpi.start] & TRANS_PROPERTY_SATISFIED)) {
-			describe_unsatisfied(trans->upstream.set, rp);
+			if (callback)
+				describe_unsatisfied(trans->upstream.set, rp,
+						     callback, data);
 			unsatisfied++;
 		}
 	}
@@ -841,6 +845,25 @@
 	return unsatisfied;
 }
 
+static void
+describe_unsatisfied_callback(const char *requirement,
+			      struct razor_package *package, const char *name,
+			      const char *version, const char *arch, void *data)
+{
+	FILE *fp = data;
+
+	fprintf(fp, "%s is needed by %s-%s.%s\n", requirement,
+		name, version, arch);
+}
+
+RAZOR_EXPORT int
+razor_transaction_describe(struct razor_transaction *trans)
+{
+	return razor_transaction_unsatisfied(trans,
+					     describe_unsatisfied_callback,
+					     stderr);
+}
+
 RAZOR_EXPORT int
 razor_transaction_unsatisfied_property(struct razor_transaction *trans,
 				       const char *name,